Talk:Photosynthesis/Archive 2

Archive 1

Archive 2

Wavelength...

In one of the last sections, "Light intensity (Irradiance), wavelength and temperature", the question of wavelength looks like it will (finally, after having been neglected the entire article) addressed. But this does not actually happen. Something needs to be added about what wavelengths are necessary for photosynthesis to work. You can't grow a plant using a typical incandescent bulb, but you can if you use a fluorescent one producing even fewer lumens. It's not simply light level and heat which is important, but also (or perhaps most importantly) frequency. This needs to be inserted, perhaps even with an additional summary near the top. Kaz 22:33, 4 January 2007 (UTC)

Algae and low-light plants (java moss, and najas grass) grow just fine in my fish tanks with just an incandescent or halogen bulb. But they grow better with a florescent bulb. Just an FYI. 64.199.9.162 (talk) 17:51, 19 January 2009 (UTC)

Wavelength is indeed important. I am surprised at the remark above! I did this experiment for a jr. high school science fair experiment. Plants use specific wavelengths to photosynthesize the rest of spectrum is useless. Think about it: all plants are some shade of green. Logically, this means that green light is being REFLECTED; the other wavelengths (perceived by the eye as colors) are ABSORBED. What colors/wavelengths, then, by logic, are being used, and which color is being discarded? Moreover, they use different wavelengths at different times of the day, indicating they are using different pathways according to the hour. This makes sense, since sunlight is richer in some wavelengths and poorer in others at different times of the day, according to the angle of the sun to the horizon, and quantity of particles in the air. Finally, there are pigments in the chloroplasts that enhance photoabsorption, notably carotenoids, which become visible when leaves die and give autumn it's wonder in deciduous forests. —Preceding unsigned comment added by 75.106.247.79 (talk) 15:04, 10 May 2009 (UTC)

Logically, what your saying may make sense but empirically it is apparently untrue. Look at: Terashima, et al., 2009. Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green. Plant and Cell Physiology, 50(4)684-697(14). This has been known for some time as Hershey wrote about this misconception in 1995 (Hershey, D. R. 1995. Photosynthesis misconceptions. American Biology Teacher 57: 198). This page should be updated to reflect this, especially the section that says photosynthesis does not use green light.Michaplot (talk) 20:35, 16 September 2009 (UTC)

Other photosynthesis

Don't humans photosynthesise vitamin D from sunlight? I originally thought it was like photo- osmosis, but that wouldn't work. I then found out that sunlight is used to make vitamin D in the skin. So using light to create things = photosynthesis. And that is what humans do. I think maybe other animals do something similar? Cheesypot 23:09, 12 January 2007 (UTC)

Quantasomes

what is called a photosystem on the page should correctly be named as a quantasomes as they are the smallest structural unit of photosynthesis on the thylakoid membrane and it is the Quantasomes which contain the chlorophyll and cytochromes.

being called a photosystem is partially correct but it is within the Quantasome that the photosystem is contained. but not the name of the actual component

the line reading "light dependent reactions occur in the thylakoid membranes of the chloroplasts"

should correctly be "The light dependant reactions occur in the quantasomes on the thylakoid membranes in the chloroplast"

and the image anatated as "A Photosystem: A light-harvesting cluster of photosynthetic pigments present in the thylakoid membrane of chloroplasts."

should be "A Quantasome: present on the thylakoid membrane, Containing the Photosystem - A light-harvesting cluster of photosynthetic pigments." —The preceding unsigned comment was added by Mauller95 (talk • contribs) 18:29, 21 January 2007 (UTC). heloo pople

Vandalism magnet

Why exactly is the Photosynthesis article semi-protected again? I mean, it's not even a religious or political topic! I can't believe that someone has a bone to pick with the idea of photosynthesis. Seriously, what the heck!? [[

H2S To Sulfur Photosynthesis / Archaea

I noticed that this article talks about the hydrogen sulfide to sulfur photosynthesis process as being performed by bacteria. However, in my poking around on the subject Encarta claims that this process is performed by the bacterialike archaea instead.

Not being anything like a biologist I can only throw this out as confusion on my part in hopes that someone could clarify. I do believe that these days the archaea are not at all regarded as bacteria, being in an entirely different family, though some do hedge and refer to them as "archaebacteria". MrG 4.227.250.35 22:56, 3 February 2007 (UTC)

Nature Paper - appearance of oxygenic photosynthesis

I Draw page author’s attention to the recent paper in Nature by Allen and Martin (Vol445, number 8, pgs610-612), titled, “Out of thin air”. It nicely reviews alternative theories for when oxygenic photosynthesis appeared on earth. They further describe a hypothetical proto-cyanobacterium expressing both types of photosynthesis, and which might still be extant. SNP 19:49, 8 February 2007 (UTC)

General Equation for photosynthesis

I just added a reference to the general equation, any disputes will be reverted unless you provide a credible source or logic (experimental evidence would be good too). -68.75.17.218

It can be confusing, but after you get it, not so much... I remember in my high school textbooks when the older, "balanced" equation was used and taught. But as a biology major, I learned that in the Calvin Cycle of sugar synthesis, the six oxygen atoms that are liberated from the plant don't come from the carbon dioxide it "breathes", but actually comes from water molecules that the plant uses as a reactant in photosynthesis. Because each water molecule has only one oxygen atom, the plant will need twelve molecules to fully complete the cycle. Later on in photosynthesis, six water molecules are also products. This occurs during carbon fixation, in which the carbon dioxide is built together into a sugar molecule and hydrogen ions are used to turn reactive oxygen atoms that go flying off into useful water molecules that can be used again by the plant as soon as the cycle completes.

In the future, you might want to add new topics on the Talk page at the bottom of the page, as that is where most users will check for the most recent additions. And you can easily sign comments by using four tildes (the ~ character) at the end of your comments. I hope this helps!--Ryan! 06:04, 5 March 2007 (UTC)

atmospheric carbon sequestration capacity

Is there any study related to the measurement of carbon absorption by plants in hydroponic cultures inside greenhouses, excluding all organic matter in the nutrient solution ? If we have on average 200ppm to 400ppm (or about 400mg of C02 per m3 of air) of carbon dioxide in the atmosphere, how much of that could be absorbed, on a daily basis, by one square meter of cultivated land? Does this absorption occur only when air passes through the leaves or are the carbon dioxide molecules attracted to the leaves' surface by some other selective "mechanism", binding CO2 molecules in something like a string that is pulled by such a process ? This question may sound silly, but if all air had necessarilly to be "filtered" by the leaves in order to allow them to absorb the CO2, this would IMO imply a less efficient process than one that could bind free CO2 molecules dispersed in a small concentration in "lots" of air and then "pull" them towards the leaves... --Dfv10 02:58, 15 March 2007 (UTC)

Corollary factors?

What is this section supposed to be about? It only consists of a header line and a stub notice, but I wouldn't even know what to put in there if I wanted to expand it. Does anyone have an idea what "corollary factors" is supposed to summarize in the context of photosynthesis? - tameeria 18:21, 3 April 2007 (UTC)

Equation

There has been the repeated addition of "catalysts" to the equation of photosynthesis now. Is there any reliable reference for that? All references I have don't list "catalysts" at all. E.g.:

• Campbell & Reece: Biology, 7th Edition:

6 CO₂ + 12 H₂O + light energy → C₆H₁₂O₆ + 6 O₂ + 6 H₂O (equation for glucose; also listed in Freeman and Brooker)

• Freeman: Biological Science, 2nd Edition:

CO₂ + 2 H₂O + light energy → (CH₂O)_n + H₂O + O₂ (general equation)

• Brooker et al.: Biology, 1st Edition:

CO₂ + 2 H₂O + light energy → (CH₂O)_n + H₂O + O₂ (general equation)

• Raven et al.: Biology of Plants, 7th Edition:

CO₂ + H₂O + light energy → (CH₂O) + O₂ (general equation)

• Berg: Introductory Botany, 2nd Edition:

6 CO₂ + 12 H₂O (+ light energy, chlorophyll) → C₆H₁₂O₆ + 6 O₂ + 6 H₂O

= Carbon dioxide + Water (+ light energy, chlorophyll) → Glucose + Oxygen + Water

While we're at it, where is the "gas", "aequous" and "liquid" in the equation coming from? Is this sourced from a particular textbook? If so, a reference should be added, but I haven't found any yet that actually list that in their equations (see above for the ones I did find). - tameeria 02:12, 25 April 2007 (UTC)

Please provide a reference when changing equations. If it is changed from what it is now, chances are high that the result is something that cannot be found in textbooks. Therefore chances are high it is going to be reverted unless a reliable, verifiable reference for the new equation is provided with the edit. - tameeria 03:07, 8 May 2007 (UTC)

Photosynthesis equations

First of all the initial equation is wrong. You can't just make oxygen and sugar from water and carbon dioxide. What you need is a catalyst. I don't know why no one else bothered to put this into their equations but it is absolutely necessary in my oppinion. I have tried to proceed the given equation by just shining light on carbonated water but it obviously doesn't work. 68.252.36.107 03:35, 8 May 2007 (UTC)

The equation is not wrong. Not all equations have the catalyst. Where is that precedent coming from? David D. (Talk) 04:14, 9 May 2001 (UTC)

tiresearch]]... ;) I can see the point you're trying to make, but unless you can provide a published reference for your equation, it is unlikely to find acceptance as it stands against several textbook equations. In general, it seems to be more conventional that biochemical reactions like this are written as just reactants and products without adding the enzymes (catalysts) to the equation of the reaction. - tameeria 04:15, 9 May 2001 (UTC)

The equation

2n CO2 + 2n H2O + photons → 2(CH2O)n + 2n H2O + n O2= sean smells bad

Glucose is NOT ever an end-product of photosynthesis

Dear Stanly

 ilike pie it smells bad, like sean. It is really unfortunate that the ancient text-book error in photosynthesis that considers glucose is the end-product of photosynthesis is again repeated here. It is important to re-affirm that glucose is never an end-product of photosynthesis. The end-product of the carbon dioxide assimilation pathway is triose phosphate, a product that is then used to produce either sucrose or starch or provide carbon skeletons for other assimilations. As the date of the 14th International Photosynthesis Congress approaches, it is crucial that we eliminate this error from the definition and from future teaching materials so that no future generations get mislead by an incorrect oversimplification of this crucial process.

Christine H. Foyer (Chair of the Organising Committee of the 14th International Photosynthesis Congress).

The above comment is most probably a bona fide intervention from a real super expert in the field. I find it very unfortunate that it has been left without a proper response. I came here to look for just this kind of comment (because of a discussion about metabolism). To my understanding the (glucose) statement should at least be weakened to say that the first energy storing molecules produced by photosynthesis are used for several different things. I will check a reasonably modern biochemistry book to see if glucose is said to ever be produced. But I really hope someone beats me to it. --Etxrge (talk) 18:19, 20 December 2007 (UTC)

Oxygen is a product of photosynthesis

Dear Colleagues

I find it hard to believe that anyone would consider oxygen to be a waste product of photosynthesis as stated in the present text. Oxygen is a true product of the process. I hope that this error can be corrected as soon as possible. Oxygen production by photosynthesis is a key component of the global oxygen cycle.

Christine H. Foyer (Chair of the Organising Committee of the 14th International Photosynthesis Congress).

It may be part of the global oxygen cycle, but it's a waste product as far as the plant is concerned (assuming a plant could be concerned with anything). Carbon Dioxide is a waste product of animal respiration, the fact that it is needed by plants doesn't change this.--RLent 17:18, 20 September 2007 (UTC)

I definitely agree with C.H. Foyer. Plants do respiration as well as photosynthesis; therefore, oxygen is not a waste product.--Chinoadidas (talk) 03:04, 7 December 2007 (UTC)

I don't understand the logic, just because it is a substrate for respiration does not mean that overall it is not a waste product for a plant or algae. It all depends on the perspective. Ecological or organismal. Don't you consider CO₂ a waste product of animals despite the fact that there are carboxylation reactions in cells? David D. (Talk) 03:18, 7 December 2007 (UTC)

Calling anything a "waste" product is a bit strange. Water is a product of respiration, but is this a "waste product"? This term has no real biochemical meaning except for such things as D-lactate, which is produced from methylglyoxal and has no further possible metabolic role in an organism. Tim Vickers (talk) 04:49, 7 December 2007 (UTC)

I agree waste sounds strange but the I can understand sentiment. Is CO₂ a waste product? I think the emphasis here is that the plant is not producing O₂ for our pleasure. Or its own for that matter. Maybe byproduct is the best description? David D. (Talk) 04:58, 7 December 2007 (UTC)

Just say "product" and be done with it, after all, below the compensation point, oxygen is consumed, not produced. Tim Vickers (talk) 05:26, 7 December 2007 (UTC)

Or more to the point at night. But still, overall the plant gives off oxygen, that is a logical rationale for using waste. Either way i think this is a minor issue. More important is to ensure the major misconception that plants do not respire is not reinforced in the confusion. David D. (Talk) 06:33, 7 December 2007 (UTC)

Very true. Tim Vickers (talk) 22:10, 7 December 2007 (UTC)

I think the problem with the word "waste" is the perception by C.H.F. and T.V. of an anthrocentric bias. On the other hand, however, D.D. is correct in pointing out that there is a scientific use of the word. Waste signifies that it is expelled by the organism, as it is either not useful for the organism, or it is produced in far greater quantities than the organism can put to use for its current and/or future needs. Thus, water is considered a waste product of respiration in mammals, even though it is necessary for other uses, and is removed by the kidneys from the blood. I think it is important to think about science in scientific terms and attempt to avoid nitpicking for the advancement of political agenda and ideologies. -SB —Preceding unsigned comment added by 75.106.247.79 (talk) 15:18, 10 May 2009 (UTC)

SB does have a point.What we are talking about here,is the concept of reactants forming products. And we are well aware of the fact that Scientific terms and words which we use in our daily life do not always mean the same.Let us just focus on the concept and understand it better instead of raising such controversies.Waste or not,oxygen is still a product..or 'a byproduct' sounds better.....!(JSR)

equations in overview

I have replaced the balanced (simplified) equations. The equations as written are what is generally seen in an introductory text (the second is cited as such). Now, if the product is written as triose phosphate, which is not C3H6O3, then the reactant side of the equation must include P. So either replace the first with a correctly balanced phosphate including equation - or leave as is in the overview and present the details later. As most readers are not biologists, keep the initial equations as the perhaps familiar ones - noting the shortcomings and continuing with the more complex equations later. Vsmith 03:09, 16 June 2007 (UTC)

Agreed. Thanks for spotting the mismatched equations. Clicketyclack 08:09, 16 June 2007 (UTC)

Potential image

I planted popcorn this year, and ten stalks were white! They were successful for a short time, then they all died - I suspect they could not perform photosynthesis properly. Is there any interest in the photographs that I took? Is there any interest in seed samples (we haven't popped all the popcorn seeds yet)? Is there such a thing as albino plants? Royalbroil 19:03, 22 June 2007 (UTC)

Neat! And yes, they are actually called "albino plants," at least in the case of Arabidopsis and barley albino seedlings, which I know are used in research. They usually die (unless grown on sugar medium) once they've used up all the resources stored in the seed because they cannot photosynthesize. The albino phenotype in plants is a severe form of chlorosis, so I think your pictures might be best placed as illustrations for that article rather than here? - tameeria 20:33, 22 June 2007 (UTC)

I was guessing that they survived until they used up the resources in the seed. I will upload an sample image and place it in the chlorosis article. Thanks for pointing me in the right direction! Royalbroil 01:34, 23 June 2007 (UTC)

Photosynth

Is it ever called "Photosynth"? Coz, if not, I am thinking of removing it from the Photosynth (disambiguation) page. --soum ^talk 07:07, 30 June 2007 (UTC)

Photosynthesis Defn

It is a complex process occurring in higher plants, phytoplankton, algae, as well...

just a question. Does it occur only in higher plants or all plants? --Muhammad Mahdi Karim 16:10, 24 October 2007 (UTC)

I think the word higher is to used to contrast it with some algae that are considered "lower plants". --Kupirijo (talk) 09:30, 10 June 2008 (UTC)

Also I am going to remove phytoplankton because it is redundant, as the words algae and cyanobacteria cover it. --Kupirijo (talk) 09:30, 10 June 2008 (UTC)

Importance of photosynthesis for technologies

Hi. Some of us are trying to work up Solar energy, currently GA, to FA. We need a good reference for the idea that all the food humans eat, wood they use, and fossil fuels they use are the products of photosynthesis. Do you know a source that mentions this? I wondered whether it might be worth adding a very brief section to the photosynthesis article about the importance of photosynthesis to humans and their technologies. Thanks very much in advance. Itsmejudith 19:24, 11 November 2007 (UTC)

I'd imagine any intro biology book says this. I have World of the Cell (Beckker et al.) here and their quote is: "Nearly all life on Earth is sustained, directly or indirectly, by the sunlight that continuously floods our planet with energy." The exception are the communities that rely on the bacteria in black smokers to sustain life. Those bacteria get all their energy from the oxidation of chemicals that comes from the black smokers. Practically none of the suns energy is used in those hydrothermal vent communities. David D. (Talk) 19:51, 11 November 2007 (UTC)

Glucose is NOT ever an end-product of photosynthesis (repeat headline from above)

From Biochemistry, by Campbell and Farrel, 2006, (Thomson Brooks/Cole), p 619, "the carbohydrates produced from carbon dioxide by photosynthesis is not glucose ...". --Etxrge (talk) 19:41, 21 December 2007 (UTC)

Most of the text is correct, it's the equations that need to be fixed. David D. (Talk) 19:47, 21 December 2007 (UTC)

wording on efficiency:

6) Efficiency: The article states: “Plants convert light into chemical energy with a maximum photosynthetic efficiency of approximately 6%.[16]”

I think it would be much more accurate to reword the above to : Plants convert total incident light energy into fixed energy storing biomass at an efficiency of 6%

The rewording is necessary because if you take the portion of the light that is absorbed by the chlorophyll more than 95% is, in fact, converted to chemical energy.

http://www.lbl.gov/Science-Articles/Archive/PBD-quantum-secrets.html

So the actual conversion of light to chemical energy is remarkably efficient, its just that : light is reflected off the leaves, much of the resultant chemical energy is used for respiration etc. , and so never makes it to stored carbohydrates .

Photosynthesis isn’t 6% efficient at turning light into chemical energy its almost 100% efficient.

Chem teacher (talk) 22:42, 19 January 2009 (UTC)

The Wikipedia article is seriously outdated in failing to mention the 2007 breakthrough in understanding how photosynthesis achieves its nearly 100% energy transfer efficiency through use of quantum coherence effects, as documented in the April 12, 2007 issue of Nature. See "Quantum Secrets of Photosynthesis Revealed" at http://www.lbl.gov/Science-Articles/Archive/PBD-quantum-secrets.html for news of this very remarkable discovery.

The Wiki article is also hilariously ridiculous in implying that our current solar panel technology is several times more efficient than photosynthesis! See the same article I cite for a projection that we can eventually develop efficient artificial photosynthesis on par with nature's by learning "huge lessons" about how photosynthesis incorporates quantum effects.

74.250.226.81 (talk) 03:00, 28 February 2009 (UTC)

Also worth note perhaps is that the 41.1% efficient cell referenced in the article, is only acheived by stacking multiple cells on top of each other. Can one really call that a cell? The second law of thermodynamics leads to the conclusion that a solar cell with a single type of light absorber cannot achieve more than 33% efficiency. —Preceding unsigned comment added by 149.171.55.188 (talk) 07:07, 21 October 2010 (UTC)

90 percent efficiency quote (reference 4) is incorrect

If you check the citation for that quote (http://www.sciencenews.org/articles/20070414/fob5.asp), you'll find that it now has an erratum posted, which says (and I quote): "This article incorrectly states that plants "use up to 90 percent of the light that strikes them." Photosynthetic organisms can use more than 90 percent of the energy they absorb, but the absorbed photons are a small percentage of those that strike an organism." This should be corrected, but I don't have an account; can someone who does please correct it? -- Brooks, 09 April 2008. —Preceding unsigned comment added by 64.81.73.35 (talk) 18:15, 9 April 2008 (UTC)

(Also, it should be noted that the sentence in question here is directly copied from the Science News article, which is of course plagiarism and needs to be fixed anyway.) -- Brooks —Preceding unsigned comment added by 64.81.73.35 (talk) 18:18, 9 April 2008 (UTC)

I've rewritten this, can you check my new version? Tim Vickers (talk) 18:27, 9 April 2008 (UTC)

Fructose is not a disaccharide

1st paragraph Overview New to contibuting so do not want to change myself. If someone/everyone agrees pleas change. Nzmach1 (talk) 18:11, 16 April 2008 (UTC)

Thank you, corrected. Tim Vickers (talk) 19:22, 16 April 2008 (UTC)

tiny typo

Molecular production,Temporal Order "The overall process of photosynthesis takes place in four stages. The first, energy tranfer in antenna chlorophyll takes place in the femtosecond " needs an "s" in transfer ... there is a lock to stop people editting

Oxygen is a product of PSII

I cannot believe that such a basic error would remain for such a long time. I have changed the sentence to be: Oxygen is a product of the light-driven water-oxidation reaction catalyzed by photosystem II

It is not a product of PSI, but of PSII.

My friend has actually used this mistake as an example of how you should have a critical approach towards Wikipedia articles. Neyne (talk) 19:43, 15 May 2008 (UTC)

Well it was there for a month after these edits. It looks more like a typo than anything and it's far from a consistent mistake throughout the article. Even textbooks have typos like this. Not that I'm trying to defend wikipedia, because it is these kinds of issues that are a real time sink with regard to maintaining the quality of articles. While text books do have errors, once they are caught they are gone for good. But at wikipedia there is a need to be forever vigilent. David D. (Talk) 04:15, 16 May 2008 (UTC)

"nearly all life on Earth either directly or indirectly depends on it."

What life does not? --AnotherSolipsist (talk) 02:52, 12 June 2008 (UTC)

Chemolithotrophic organisms, such as the bacteria and tube worms around hydrothermal vents. Tim Vickers (talk) 04:32, 12 June 2008 (UTC)

Even organisms near hydrothermal vents are subject to the carbon flux delivered from higher in the water column. Interestingly, even some of the bacteria that live near hydrothermal vents are obligately photosynthetic. (Beatty et al, PNAS 102:9306 2005). The best argument for life independant of the sun comes from bugs found in isolated waters in South African gold mines, which manage to live on hydrogen produced by radioactivity. It has not been shown, though it is believed to be the case, that they fix their own carbon so we do not know whether they are independent or not. 205.214.48.251 (talk) 20:00, 28 October 2008 (UTC)

While they are obligately photosynthetic they do not get their light from the sun. While the question did not specifically mention the sun I suspect that type of photosynthesis is what they had in mind. Also the vent community is unlikely to rely on the photosynthetic bacteria even though they do exist there. The pertinent question here is not if carbon from the top can enter the system, clearly it can, but is the system sustainable with zero energy and carbon input from above. I believe it is from what i have read. David D. (Talk) 07:06, 29 October 2008 (UTC)

Photosynthesis is when a plant uses the light energy from the sun to help make a sugar in order for the plant to live. —Preceding unsigned comment added by 71.167.96.243 (talk) 01:34, 20 November 2008 (UTC)

Introduction picture?

Now don't get me wrong, a picture of a leaf is great, but wouldn't the diagram of the whole process of help people better understand the whole process of photosynthesis better than a picture of a leaf? 98.166.139.216 (talk) 22:48, 25 November 2008 (UTC)

There is a picture of the whole process in the overview section. I think the picture fits better in that place. {Kasper90 (talk) 08:46, 4 January 2009 (UTC)}

Thanks for actually responding Kasper90 . Your efforts to communicate with anonymous editors like me are greatly appreciated. 98.166.139.216 (talk) 22:00, 12 January 2009 (UTC)

Since there are several possible pathways, what about the primary productivity picture? Tim Vickers (talk) 22:23, 12 January 2009 (UTC)

Algae/bacteria

" It is a complex process occurring in plants, algae, as well as bacteria such as cyanobacteria. " I think it should be: "occuring in plants and algae, like cyanobacteria" Because cyanobacteria are algae, right? or am I wrong? Kasper90 (talk) 13:39, 7 January 2009 (UTC)

Cyanobacteria are a group of bacteria, algae are a poorly-defined group of eukaryotes (protists). Tim Vickers (talk) 17:11, 7 January 2009 (UTC)

Jeah, I just read it.

"Though the prokaryotic Cyanobacteria (commonly referred to as Blue-green Algae) were traditionally included as "Algae" in older textbooks, many modern sources regard this as outdated[4] and restrict the term Algae to eukaryotic organisms.[5]"
I think the dutch algae article is outdated then. Kasper90 (talk) 03:26, 8 January 2009 (UTC)

Quantum section

Moved to talk, seems to have too much text relative to the rest - might be summarised in a sentence later. Tim Vickers (talk) 22:25, 11 January 2009 (UTC)

Quantum mechanical effects

Through photosynthesis, sunlight energy is transferred to molecular reaction centers for conversion into chemical energy with nearly 100-percent efficiency. The transfer of the solar energy takes place almost instantaneously, thus little energy is wasted as heat. Of the total incident solar radiation only 43% can be used (only light in the range 400-700 nm), 80% of light makes it through the canopy, photosynthesis stores 28.6% of the energy, and plant respiration uses some energy which leaves 67% of the stored energy behind. This brings the actual efficiency of photosynthesis to about 6.6%.

A study led by researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley suggests that long-lived wavelike electronic quantum coherence plays an important part in this instantaneous transfer of energy by allowing the photosynthetic system to simultaneously try each potential energy pathway and choose the most efficient option.

=

Oxygen is produced in light-dependent reactions

"Oxygen is a waste product of light-independent reactions"

It should be 'light-dependent'.

86.106.193.108 (talk) 22:18, 3 February 2009 (UTC)

Corrected. Thank you. Tim Vickers (talk) 22:27, 3 February 2009 (UTC)

Energy trapped by photosynthesis

Please replace "100 terawatts per year" with just "100 terawatts". The unit "watt" is already an energy rate. I see that the original source mentions 100 TW/year so I'm not sure if we can trust it, but they do also mention incoming solar radiation to be 178,000 TW/year which is correct if you remove the "/year".

Also replace "which is about seven times" with "which is about six times". (100/16 = 6.25).

I would have done the changes myself but this page is semi-protected. —Preceding unsigned comment added by 24.6.174.244 (talk) 21:26, 8 February 2009 (UTC)

Done. --Michael C. Price ^talk 10:00, 27 March 2009 (UTC)

The statement as currently published is: The amount of energy trapped by photosynthesis is immense, approximately 100 terawatts:[3]...

The wikipedia article on the watt, http://en.wikipedia.org/wiki/Watt, begins with the statement: The watt... is a derived unit of power... And later it says: Power and energy are frequently confused. Power is the rate at which energy is generated and consumed.

So the first statement I quoted from the article equates energy with terawatts, but terrawatts are a measure of power not energy. However if we go to the wikipedia article on Kilowatt hour, http://en.wikipedia.org/wiki/KWh, we have the statement: The kilowatt hour, or kilowatt-hour... is a unit of energy...

I believe this means the ORIGINAL version of the article, with the reference to "terrawatts per year" - which is simply killowatt hours on a different scale - is the version with the correct units. I make no statement about how close the quantities quoted are to being correct, but I do know that the most basic requirement is to get the units correct, and right now they are wrong.

Sorry if I am not up on the details of wikipedia procedures, I'm just a guy who noticed a problem. —Preceding unsigned comment added by 64.252.115.164 (talk) 20:53, 11 May 2010 (UTC)

Both original and current statements are wrong (TW/year and kW.h are not compatible). If I calculate correctly the "six times" figure is also wrong: world energy consumption for 2006 according to reference is 473*10¹⁵Btu = 139*10¹⁵W.h = 139000000TW.h = 15868TW.year. --Nk (talk) 14:00, 15 July 2010 (UTC)

C6H12O6

Anybody else think that searching C6H12O6 should deliver you to the page on glucose, not the one on photosynthesis? 76.181.227.217 (talk) 23:32, 5 April 2009 (UTC)

C6H12O6 seems to go to a disambiguation page for hexose sugars when I type it in. Vsmith (talk) 00:35, 6 April 2009 (UTC)

Checked again. The messed up link was actually when a zero was mistakenly typed in place of the letter "o". 76.181.227.217 (talk) 23:29, 6 April 2009 (UTC)

Lead section

Although the lead sectionis much better than it ever was, I still think it is not really what it should be...

As written in Wikipedia:Lead section: "In general, specialized terminology should be avoided in an introduction. "

Terms as organic compounds, Archaea, source of Carbon, might not be really specialized terms but rather simple biology terms, but many people who will try to read this introduction just want to know what photosynthesis basically is and how it affects our life every day. It should be about the difference between autotrophs and heterotrophs and not about the difference between photoautotrophs and photoheterotrophs in my point of view. Kasper90 (talk) 07:19, 27 May 2009 (UTC)

We need to replace 3,500 million years, in the lead article, with 3.5 billion years instead. — Preceding unsigned comment added by 75.54.70.113 (talk) 11:14, 13 January 2012 (UTC)

Carbohydrates vs organic compound

What else then carbohydrates are made by photosynthesis, because I thought it was 'only' carbohydrates and not 'especially', as written in the first sentence of this article. 58.147.45.79 (talk) 12:40, 27 May 2009 (UTC)

Thermosynthesis

I reverted this edit since I can't find any good sources discussing the evolution of photosynthesis from thermosynthesis. Can anybody else find any, none of the reviews I've read on photosynthetic evolution have mentioned this idea. Tim Vickers (talk) 15:36, 22 June 2009 (UTC)

When cyanobacterial symbiosis began

The line "Eventually, about 550 million years ago, one of these protists formed a symbiotic relationship with a cyanobacterium, producing the ancestor of the plants and algae.[8]" is found word-for-word all over the Internet, yet the reference [8] doesn't say 550 millions years. It says about a billion. I've fixed it. Note that the 550M contradicts a claim made in the algae article that algae appears 1.6-1.7B years ago. You can search on research title "Megascopic eukaryotic algae from the 2.1-billion-year-old negaunee iron-formation" and "Lichen-like symbiosis 600 million years ago" for more. —Preceding unsigned comment added by Cdorman2 (talk • contribs) 18:17, 26 August 2009 (UTC)

Thanks, I've shuffled the refs around a bit as well. Tim Vickers (talk) 19:08, 26 August 2009 (UTC)

Illustration of overall process

Some suggestions for the jpg near the start of the article (http://en.wikipedia.org/wiki/File:Photosynthesis.jpg)

1 Change the word "formula" in the caption. The jpg shows an equation (more fully, an overall equation for a process).

2 Delete the reverse arrow, which is for aerobic cellular respiration.

3 Replace "cellulose" with the correct translation of "bladgroen", which is "chlorophyll".

Dasyornis (talk) 06:41, 20 October 2009 (UTC)

Thank you, I've fixed it. Tim Vickers (talk) 17:29, 3 February 2010 (UTC)

Light reaction

Is the ATP yield 2 or 3? I've found sources that say both. Tim Vickers (talk) 17:25, 3 February 2010 (UTC) it is used by damodar pyakurel. my gmail id iis jam.davidpack70@gmail.com —Preceding unsigned comment added by 99.37.214.184 (talk) 00:40, 23 February 2010 (UTC)

To my knowledge it differs between organisms, and is dependent on the H/ATP ratio and the size of the C-ring. They are (exclusively i believe) non-integers due the C-ring usually being non-divisible by 3. Silasmellor (talk) 10:49, 2 April 2010 (UTC)

Regulation of photosynthesis

I suggest a section be added concerning the regulation of photosynthesis (possibly merged with the photosynthetic efficiency section), with a brief description of the types of measures used by photosynthetic organisms to maximise efficiency/minimise unfavorable side reactions. Silasmellor (talk) 10:47, 2 April 2010 (UTC)

Big oopsie

You should not include evolution, because, well, it's not real. Most people would take this as even more proof of a Creator, how could something so "simple" have such an amazing way to create its own food by chance? —Preceding unsigned comment added by 173.30.89.138 (talk) 18:28, 16 June 2010 (UTC)

see Talk:Evolution/FAQ. Tim Vickers (talk) 18:46, 16 June 2010 (UTC)

Edit request from 94.1.19.210, 18 June 2010

there is a rude insert in the article saying: if you read this you will die in 2 days ... Please remove it. 94.1.19.210 (talk) 18:24, 18 June 2010 (UTC)

That's already been removed. Thank you though. Tim Vickers (talk) 18:31, 18 June 2010 (UTC)

A little more information please

The opening paragraph says:- "The rate of energy capture by photosynthesis is immense, approximately 100 terawatts:[3]" is this per day, per week, per month or per year? Unless this is stated the sentence is meaningless. Could someone fill in this vital blank please? Thanks. SmokeyTheCat 19:36, 11 September 2010 (UTC)

Unfortunately citation #3 in the above quotation is not free, but based on this link, it appears that the unit of time is "per year". Boghog (talk) 20:09, 11 September 2010 (UTC)

As an IP has pointed out, watts are a unit of power and "shouldn't have a time-base reference". It would be interesting to know how many terrawatt hours of energy photosynthesis produces each year - currently the article makes no mention of joules. Smartse (talk) 09:48, 22 September 2010 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Photosynthesis/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Comment(s)

Press [show] to view →

6) Efficiency: The article states: “Plants convert light into chemical energy with a maximum photosynthetic efficiency of approximately 6%.[16]” I think it would be much more accurate to reword the above to : Plants convert total incident light energy into fixed energy storing biomass at an efficiency of 6% The rewording is necessary because if you take the portion of the light that is absorbed by the chlorophyll more than 95% is, in fact, converted to chemical energy. http://www.lbl.gov/Science-Articles/Archive/PBD-quantum-secrets.html So the actual conversion of light to chemical energy is remarkably efficient, its just that : light is reflected off the leaves, much of the resultant chemical energy is used for respiration etc. , and so never makes it to stored carbohydrates . Photosynthesis isn’t 6% efficient at turning light into chemical energy its almost 100% efficient. Chem teacher (talk) 22:32, 19 January 2009 (UTC)

Last edited at 22:34, 19 January 2009 (UTC). Substituted at 21:54, 3 May 2016 (UTC)

Archive 1

Archive 2

"Injured air"?

In the Discovery section on Joseph Priestly it says that he discovered a candle or a mouse in a sealed container could "injure" air. This may work as a simple explanation, but his belief was that the air became saturated with "phlogiston" which was incompatible with life or fire. His idea was that plants "dephlogisticated" the air by absorbing it (When he discovered oxygen he called it "dephlogisticated air"!)http://www.jimloy.com/physics/phlogstn.htm I think this should be changed because it's more accurate and shows what people thought photosynthesis involved back then. Silenceisgod (talk) 15:49, 12 December 2010 (UTC)

Edit request from 74.83.221.83, 14 March 2011

{{edit semi-protected}} can i edit

74.83.221.83 (talk) 00:41, 14 March 2011 (UTC)

Not done: please be more specific about what needs to be changed. There are two ways you can edit the page. One is to register an account; after 4 days and 10 edits to non-protected pages, you will automatically be configuration

do not wish to create an account, you may use edit requests like this one to request specific changes.  When you do so, you'll need to explicitly state what needs to be changed, why, and, if appropriate, provide a reliable source to support your requested change. If you have any general questions, feel free to ask me on my talk page at any time. Qwyrxian (talk) 04:44, 14 March 2011 (UTC)

Disambiguation needed

In the "Carbon dioxide levels and photorespiration" section, the end of numbered paragraph 3 links to diffuse, which redirects to diffusion (disambiguation). This should be changed to link to the specific type of diffusion, but I'm not sure which of the many entries on that dab page is the correct one. Thryduulf (talk) 15:34, 19 April 2011 (UTC)

Students

They got confused since there is specially brought out C4 and CAM but nothing directly indicates to C3. Ty --193.40.25.251 (talk) 13:53, 27 April 2011 (UTC)

Edit request from 14.98.95.115, 17 June 2011

No information is given about the time duration in capturing 100 terawatts of energy by plants. So please mention it.

14.98.95.115 (talk) 08:57, 17 June 2011 (UTC)

You're confusing energy with power. Or joules with watts. -- cheers, Michael C. Price ^talk 09:47, 17 June 2011 (UTC)

in the article it states that 100 thousand million watts is 100 terawatts. 100 terawatts is 100 million million watts not 100 thousand million watts. 100,000,000,000,000 is 100 trillion as the standard counting system goes: thousand, million, billion, trillion. these numbers change as they become prefixes to messurement, they become: kilo, mega, giga, tera. i believe that i am correct in saying that the estimate for photosynthesising power is 100 thousand BILLION watts as a posed to 100 thousand Million watts. please correct me if i'm wrong. — Preceding unsigned comment added by 2.27.71.134 (talk) 14:47, 6 January 2013 (UTC)

The article states that rate of global photosynthetic energy capture is "130 terawatts" while "100–115 thousand million metric tons" of carbon is fixed by photosyntheis per year. These figure refer to two distinct quantities. Rate of energy capture should not be confused with weight of carbon fixed. Boghog (talk) 15:02, 6 January 2013 (UTC)

you're right i'm not sure how i got that so muddled up. soory — Preceding unsigned comment added by 2.27.71.134 (talk) 15:19, 6 January 2013 (UTC)

Misslabled graph

The labels on the axis of the graph of carbon absorption vs radiance are reversed. Dauto (talk) 18:33, 9 September 2011 (UTC)

I could edit the graph but commented it out instead, as it is unreferenced and unexplained (units on the X axis, for example). Materialscientist (talk) 22:25, 9 September 2011 (UTC)

... times larger than ...

Does "six times larger than" mean "seven times as large as"? If so, I suggest that "seven times as large as" would be clearer. Jack Waugh (talk) 03:53, 14 September 2011 (UTC)

Times means multiply (by the given number), thus no ambiguity. Materialscientist (talk) 03:56, 14 September 2011 (UTC)

You skirted my question. Jack Waugh (talk) 20:38, 13 July 2012 (UTC)

I agree with Jack. The point at issue is not the multiplication operation, but which multiplication was applied. "...times larger than..." is not a meaningful, let alone elegant, construction. If you doubt this, take it to extremes. How do you like twice large than? How about once larger than? Half larger than? Sloppy, sloppy!  ;-) JonRichfield (talk) 06:12, 14 July 2012 (UTC)

I agree. a percentage may also be used to explain this: 100% more = twice as much = once more than therefore 600% more still fits closely to the articles original wording but i believe to be clearer — Preceding unsigned comment added by 2.27.71.134 (talk) 14:51, 6 January 2013 (UTC)

... why page rankings are completely worthless ...

This page demonstrates it perfectly. The article is both comprehensive and detailed, includes excellent diagrams, many references to the literature, and is generally well organized and written. But look at the ratings--all of them just slightly above average. This is almost certainly due to clowns voting who really have no idea what they're doing. I've seen a number of pages like this now. It's a joke. Jeeb (talk) 19:31, 5 January 2012 (UTC)

WHY it doesn't help:

This is another article which explains nothing to anyone who doesn't already know it. One "talker" says the ratings are pointless due to stupid people who don't know what they are talking about. My point exactly... the articles are written as if people should ALREADY KNOW IT ALL. Too many people with their noses in the air. If you are smart enough to understand scientific terminology written by someone who doesn't have a CLUE how to write for the LAYPERSON, then what the heck are you doing at WIKIPEDIA? I need to know about photosynthesis, but the author of this article wasn't interested in teaching me, only in showing off high level vernacular. Thanks anyway, you can keep Wikipedia, no wonder everyone is telling me it's a useless site for learning. College professors said to stay away from it. Now I understand. 108.79.61.133 (talk) 05:37, 21 April 2012 (UTC)

terrawatts

The terrawatt statement is confusing. Are they comparing the power conversion of photosynthesis for all photoautotrophs on earth? The way it is phrased, it isn't obvious if it is talking about some property of the process itself or an aggregate statistic of creatures that use the process. I'm guessing that it is talking about all life. It should say this. 75.84.186.29 (talk) 03:00, 1 July 2012 (UTC)

This might be contentious, but I'm going to take the statement out. I checked the source listed and it said the total energy consumption of all biota on earth is 100 TW. Biota includes a lot of organisms that are not photosynthetic. It may well be the case that most of the energy is from photosynthesis, but if the authors' in the source don't conclude that, I don't think that we can without original research. If we want to say something similar to what was originally said, we should look up how many joules go into each reaction, and compare it to other common chemical reactions. (Respiration, combustion, etc...) 75.84.186.29 (talk) 03:25, 1 July 2012 (UTC)

Please take another look at the source, and in particular table 1 which lists the "energy used for photosynthesis" @ "100 TW/year". The source also states that "it is estimated that the yearly global consumption of energy by the entire biota of earth today totals only 100 TW". Since these two approximations are roughly equal strongly implies that a high percentage of the energy used by life on earth originates from photosynthesis. In addition the same source states "phototrophic, light-using organisms have the upper hand in terms of energy harvesting" which is also consistent with photosynthesis supplying the majority of energy used by life. The source is not as clear as it could be, but it does not require any synthesis to come to this conclusion. Finally, it is stated earlier in the lead of this Wikipedia article that "photosynthesis is the source of energy for nearly all life on earth". This statement is supported by a reliable independent source.

The statement "The rate of energy capture by photosynthesis is immense, approximately 100 terawatts / year" IMHO is very clear. It means that the total rate of energy capture in the form of glucose by photosynthetic organisms is 100 terawatts / year. Furthermore part of the 100 terawatts / year is used directly by photosynthetic organisms and part by other organisms that feed on photosynthetic organisms. Therefore 100 TW/year is both a "property of the process itself" (the total rate of energy capture) and "an aggregate statistic of creatures that use the process" (what is done with that energy). Those two figures are equal to each other. Boghog (talk) 06:51, 1 July 2012 (UTC)

Fair enough, I missed that table, but as other users have noted(previous comments), TW/year is not a meaningful set of units for a rate.(as some have suggested, and I agree, this unit mistake makes me somewhat suspicious of the source) The author probably meant TW.h/year, which would be a common,standard measure of energy consumption. But I stand by my original claim, it should say photosynthesis of all life on earth, not just photosynthesis. This is ambiguous in the sense that each photosynthetic process, each reaction has a conversion rate which could be measured in watts. So it is important to distinguish whether you're talking about a single reaction, a mole of reactions in solution, or all reactions on the planet at some point in time.75.84.186.29 (talk) 21:01, 1 July 2012 (UTC)

Thanks for pointing out the problem with the units which I have (re)corrected in the article. Also it should be obvious that the 100 terawatt figure applies to global rate of photosynthetic energy capture, but just to make that absolutely clear, it is now explicitly stated in the article. Boghog (talk) 05:46, 2 July 2012 (UTC)

A unit that would make sense is TWh/year. It is unfortunate that the author did not use that unit, when that is probably what they meant. Terawatts, for the claim being made, strikes me as extremely dubious, which is why I removed the sentence in the first place. For example, a powerful laser can have power output in the Terrawatt range. Are we trying to say that all life on earth converts power at the rate of a laser? Note also the number that it is compared to, to get the "six times" number in cite 4, is a measure of total energy consumed per anum(BTUs/year), not an instantaneous rate of power consumption(TW). While BTUs/yr is basically the same type of measurement TWh/yr.

But I'm also not sure why the claim is there in the first place. Generally, a text on biology or chemistry addressing the topic of photosynthesis would use the molar enthalpy to compare it to another process. Searching the article, I can't find anything on enthalpy. (It shows "+ photons", when a better equation would list a certain amount of energy in kJ/mol) Is there a list that I can place this article on so that we can get some more eyeballs on this issue? It bothers me that there is almost certainly a major error in the first paragraph of an article as foundational as "photosynthesis".75.84.186.29 (talk) 06:33, 2 July 2012 (UTC)

One other note, perhaps I should have said this first. If the author meant TWh/yr and we put TW, then the number posted will be off by a multiple of ~8765.8. So we really need to find out which one they meant or we need to remove the citation. 75.84.186.29 (talk) 19:13, 2 July 2012 (UTC)

Concerning the power output of lasers, see this discussion. High energy lasers concentrate energy in extremely short pulses so while the peak power output is very high, the total energy contained in one pulse is very modest. Expressing the energy captured by photosynthesis per mole (of glucose?) is a completely unnecessary complication. The comparison of the rate of energy capture by photosynthesis in the lead is not with other chemical reactions but rather with total human power consumption. Expressing global rate of photosynthetic energy capture in units of terawatts is very appropriate in this context while stating the annual global Gibbs free energy captured by photosynthesis in units of kJ/mol would be totally confusing. One would then need to multiply by the number of moles of glucose produced globally by photosynthesis to arrive at the total energy captured. Why make things so complicated? Boghog (talk) 21:21, 2 July 2012 (UTC)

The 100 TW estimate is correct and is supported by multiple independent reliable sources:

• Steger U, Achterberg W, Blok K, Bode H, Frenz W, Gather C, Hanekamp G, Imboden D, Jahnke M, Kost M, Kurz R, Nutzinger HG, Ziesemer T (2005). Sustainable development and innovation in the energy sector. Berlin: Springer. p. 32. ISBN 3-540-23103-X. The average global rate of photosynthesis is 130 TW (1 TW = 1 terawatt = 10¹² watt){{cite book}}: CS1 maint: multiple names: authors list (link)
• Klitgaard KA, Hall CAS (2011). Energy and the Wealth of Nations: Understanding the Biophysical Economy. Berlin: Springer. p. 237. ISBN 1-4419-9397-5. The amount of energy trapped by photosynthesis is immense, roughly 3,000 exajoules/year, which is about six times larger than the energy use of all human activities (488 exajoules/year). (100 TW = 0.0001 EJ/sec, 0.0001 EJ/sec X 31,556,900 sec/yr = 3,156 EJ/year)}}

The 100 TW figure refers to the instantaneous rate of energy capture expressed in joules per second (i.e., watts). The author does not mean 100 TW*hr/year and the figure is not off by a multiple of ~8765.8. What the author meant is the rate of energy capture averaged over one year is 100 TW. Boghog (talk) 05:03, 3 July 2012 (UTC)

Note that the 100 TW figure is inconsistent with this article: http://en.wikipedia.org/wiki/Photosynthetic_efficiency Which suggests a figure between 1500 & 2250 TW.

With respect to lasers, my point was that the current phrasing does not distinguish between an average rate and an instantaneous rate. You'll note that the wikipedia article on human power consumption is very careful to always specify that rates in terawatts are an average. http://en.wikipedia.org/wiki/World_energy_consumption Failure to do so is an error IMO. A unit like TWh/yr is helpful specifically because the unit itself suggests an average rate.

I'm not sure how the molar enthalpy is an unnecessary complication.(or something similar) This is how chemical reactions are described and it is a property of the process of photosynthesis. The total rate of energy capture for all life on earth is less a statement about the process of photosynthesis and more a statement about life in general. The amount converted will vary based on factors that have nothing to do with photosynthesis, like deforestation and the average rate of solar output. It strikes me as a sort of fluff number, at best, tangentially germane. 128.97.68.15 (talk) 20:18, 5 July 2012 (UTC)

p.s. Does it bother you that the 2012 textbook citation appears to be ripped off from this article almost word for word?128.97.68.15 (talk) 20:29, 5 July 2012 (UTC)

The 100 TW statement is supported by multiple reliable sources. Wikipedia itself is not reliable source per WP:CIRCULAR. The burden of proof is on you to supply reliable sources to refute the sources that I have supplied and so far you have supplied none. Boghog (talk) 21:15, 5 July 2012 (UTC)

It is implied that the global rate of energy capture by photosynthesis is an average. In addition, the 100 TW rate is described as approximate in the lead so that even after allowing for intra-day and intra-annual fluctuations in the rate (and for that matter deforestation and fluctuations in solar output), the statement is still correct. One could explicitly state that the rates of photosynthetic energy capture and human energy production are both averages, but the wording becomes awkward and it merely states the obvious. Mentioning the global rate of photosynthetic energy capture and comparing it to human power consumption puts photosynthesis in perspective and has enormous societal implications. The global rate of energy capture is a single number. Photosynthetic pathways and efficiencies differ somewhat between different organisms (or even in the same organism under different conditions) hence there is no single chemical reaction scheme and consequently there is no single change in Gibbs free energy that can be assigned to the photosynthetic process. The idiom "not see the forest for the trees" is especially apt in this context. Boghog (talk) 05:39, 6 July 2012 (UTC)

Extended discussion about sources

The photosynthetic efficiency article which states that the rate is between 500 and 2250 TW cites: Pisciotta JM, Zou Y, Baskakov IV (2010). "Light-dependent electrogenic activity of cyanobacteria". PLoS ONE. 5 (5): e10821. doi:10.1371/journal.pone.0010821. PMC 2876029. PMID 20520829.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link) which in turn cites: Waterbury JB, Watson SW, Guillard RRL, Brand LE (1979). "Widespread occurrence of a unicellular, marine, planktonic, cyanobacterium". Nature. 227 (5694): 293–294. doi:10.1038/277293a0.{{cite journal}}: CS1 maint: multiple names: authors list (link) Note that the source above uses a much more indirect method of estimating the rate of photosynthetic energy capture (and therefore more prone to error) compared to the method used to arrive at the 100 TW estimate. The following source provides details on how they arrive at a 127 TW estimate of the global rate of photosynthetic energy capture: Whitmarsh J, Govindjee (1999). "The photosynthetic process". In Singhal GS, Renger G, Sopory SK, Irrgang KD, Govindjee (ed.). Concepts in photobiology: photosynthesis and photomorphogenesis. Boston: Kluwer Academic Publishers. pp. 11–51. ISBN 0-7923-5519-9.{{cite book}}: CS1 maint: multiple names: editors list (link) which in turn cites Houghton RA, Woodwell GM (1989). "Global climatic change". Scientific American. 260: 36–44. 100 x 1015 grams of carbon/year fixed by photosynthetic organisms equivalent to 4 x 1018 kJ/yr = 4 x 1021J/yr of free energy stored as reduced carbon (4 x 1018 kJ/yr) / (31,556,900 sec/yr) = 1.27 x 1014 J/yr (1.27 x 1014 J/yr) / (1012 J/sec / TW) = 127 TW The above estimate of the grams of carbon/year fixed by photosynthesis is consistent with the following very recent estimate (although this latest source has revised the estimate upwards by ~25%): Welp LR, Keeling RF, Meijer HA, Bollenbacher AF, Piper SC, Yoshimura K, Francey RJ, Allison CE, Wahlen M (Sep 2011). "Interannual variability in the oxygen isotopes of atmospheric CO2 driven by El Niño". Nature. 477 (7366): 579–82. doi:10.1038/nature10421. PMID 21956330.{{cite journal}}: CS1 maint: multiple names: authors list (link) Hence the most accurate and up to date estimate would be 127 x 1.25 = ~160 TW which is much closer to the estimate currently stated in this article compared to to the photosynthetic efficiency article. Boghog (talk) 14:44, 6 July 2012 (UTC)

• RFC Response An RFC was started but there doesn't appear to be a concise and neutrally worded statement on what the RfC is about. Please see Wikipedia:RFC#Request_comment_through_talk_pages, and what should be done before requesting an RfC: Wikipedia:RFC#Before_requesting_comment. IRWolfie- (talk) 16:11, 7 July 2012 (UTC)

Arbitrary break

Concerning question of whether it is preferable to report the global rate of photosynthetic energy capture ("macroeconomics") or the thermodynamics of individual photosynthetic reactions ("microeconomics"), there is no logical reason why both cannot be reported. The global rate is important since it puts into perspective the total rate of energy captured photosynthetically versus the rate of human energy consumption. It is also important to give an idea of the immense scale of global photosynthetic capture. The "microeconomics" are much more complicated to report since there is no one single photosynthetic pathway. In addition, a general audience is far more likely to be interested in the "big picture" number (how much power is captured globally by photosynthesis) than some thing as esoteric as the free energy of change when one mole of glucose is synthesized by photosynthesis. Hence per WP:MOSINTRO, the "big picture" number belongs in the lead where as details of the thermodynamics of photosynthesis belong in the body of the article.

The global rate of photosynthetic energy statement currently in the article is accurate, clear, and relevant. Hence it belongs in the article. If someone wants to in addition add details about the thermodynamics individual photosynthetic reactions, please do, but this should supplement and not replace the statement about the global rate. Boghog (talk) 18:10, 6 July 2012 (UTC)

In this edit, I have now specified that the "rate of energy capture by photosynthesis globally" is an average. I have also added citations to Whitmarsh_Govindjee_1999 and Steger_2005 to further support this estimate and revised upward the rate of energy capture upwards from 100 TW to 130 TW per the added citations. The original Nealson_Conrad_1999 citation I believed rounded the estimate of 130 TW down to 100 TW. After rounding, all three estimates are in agreement with each other. Boghog (talk) 07:19, 7 July 2012 (UTC)

The following might be worth adding to the article:

Thermodynamics of photosynthesis

According to Whitmarsh_Govindjee_1999: "The standard free energy for the reduction of one mole of CO2 to the level of glucose is +478 kJ/mol." (note that this is the net result of the Z-scheme + Calvin cycle) per mole of CO2 fixed: CO2 + 2H2O → [CH2O] + O2 + H2O (ΔG° = +478 kJ/mol) per mole of glucose synthesized: 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O (ΔG° = +2,870 kJ/mol) The above reactions are not unique to photosynthesis (in fact the reverse reaction is identical to the complete oxidation of glucose). What is unique about photosynthesis is that these endothermic reactions are driven by the energy contained in photons. The photosynthesis of a mole of glucose requires 18 equivalent of ATP and 12 equivalents of NADPH which in turn requires 54 equivalents of photons (i.e., the quantum yield per Skillman_2008 for C3 plants is φ = 0.111; 1/φ = 9 equivalents of photons per mol of CO2 fixed, 9 x 6 = 54 equivalents of photons per mole of glucose synthesized). A mole of photons with λ = 680 nm (corresponding to the absorption maxima of the P680 pigment in photosystem II) has an energy of 176 kJ/mol, or 9,504 kJ/54 mol. Hence the maximum theoretical efficiency of photosynthesis is 100 X 2,870/9,504 = 32%. (note: Bolton & Hall estimate the maximum efficiency at only 13%; I don't have access to full article at the moment, so I don't know why there is a discrepancy) The real world efficiency that plants achieve is an order of magnitude lower (on the order of 4%). Skillman JB (2008). "Quantum yield variation across the three pathways of photosynthesis: not yet out of the dark". J. Exp. Bot. 59 (7): 1647–61. doi:10.1093/jxb/ern029. PMID 18359752. Bolton JR, Hall DO (1991). "The maximum efficiency of photosynthesis". Photochemistry and Photobiology. 53 (4): 545–548. doi:10.1111/j.1751-1097.1991.tb03668.x. The theoretical maximum efficiency of conversion of light to stored chemical energy in green-plant type (oxygen-evolving) photosynthesis in bright sunlight is calculated to be 13.0%. {{cite journal}}: Unknown parameter |dat= ignored (help)</ref>

• Comment A few points. Having read much of the foregoing, I am not immediately going to propose wording, nor even to adjudicate points made. But I would like to see reactions to:

• Watts per year or per hour or per microsecond don't got nuttin' to do with the price of nitpickings. Leave all that out unless there is a need to refer to a fixed production in some fixed period (or a change of rate, which is what some of that really meant! TW/y for goodness' sake!) What matters is the rate. Even Watt-hours per year don't matter in most contexts. Stick to a few major basic (and simple for the luvva Mike!) concepts: the wattage of solar radiation that Earth intercepts, the fraction that is notionally useful to photosynthesisers (not much in fact), and the amount that effectively gets used (also not much). If you really, really, really want to deal with amounts of energy rather than rates, then the logical figure to use is Terawatt-years, which if divided by a year, gives you ... errr ... (slide rule...) oh yes! Terawatts.
• Given the wattage, what happens to it after it vanishes into the electron cascade does not change the total amount of captured energy, only how it gets sliced up.
• The amount of energy in the solar radiation at the point of its reaching the Earth's surface can be estimated to be roughly 1 kw/sq metre of the planetary cross-section. That is about pi*6000000^2 kw, or about 110000 TW, if the back of my envelope (or brain) doesn't need new batteries. Now, that is something like 1000 times as much as the estimates shown here for what enters the metabolic chain of living creatures, if there is not too much cloud.
• If that estimate is worth a belch in a parliamentary debate, then I am a pathological pessimist or even a cynic. The light at the point just below the sun (noon somewhere in the tropics) is so intense that a lot of what hits a chloroplast gets wasted. Most of the light, even in regions that show green in aerial photos, hits the ground and re-emerges as not-very useful IR. The twilight at the limb of the planet is too weak for efficient photosynthesis. Only a fraction of the light that hits any leaf is useful, and even that is at a lowish percentage of efficiency. Now, I know well that there are estimates and calculations of all those factors, but if anyone believes that all that translates to the suggested 0.1% of our solar input, please don't try to sell me a second-hand car!

Bottom line If we are to be posting believable, let alone reliable, figures in WP, I would like something better than the refs that folk have been posting in this discussion. OK, so I am a pessimist, but part of our job is to comfort and console pessimists for the misery of their existence, and in this case a bit more homework would be an encouraging and a wholesome thing say I. JonRichfield (talk) 08:37, 11 July 2012 (UTC)

On your first four points, I completely agree. (1) The rate of photosynthetic energy capture should simply be reported as terawatts and not terawatts*hr/yr. (2 &3) What is being reported is the rate of energy capture and much of what happens to that energy afterwards is not productively used because of inefficiencies in both photosynthesis as well as metabolism. (4) Of course a lot of the light that hits a leaf of a plant is not even absorbed by chlorophyl so estimating efficiency becomes very messy. Concerning the bottom line, estimates of global rate of energy photosynthetic capture based on the amount of carbon fixed are reasonably accurate and the citations that support this figure are of high quality. Finally the efficiency estimates are a lot more difficult to make because there are different ways of defining efficiency (e.g., total light that strikes the plant, light of the right wavelength the strikes the plant, light that is actually absorbed by chlorophyl, etc.) Boghog (talk) 09:27, 11 July 2012 (UTC)

Sounds fair enough to me. But then I have lost track. The current statement in the article seems unexceptionable and if we are within an order of magnitude of a reasonable estimate, what are we complaining about? (Mind you, if photosynthesis is only six time greater than our current energy usage, I am shocked and we are in trouble! I reckon that our energy usage during the 20th century alone must have risen by about that ratio! Where do we go from there? Nukes or space power?) JonRichfield (talk) 11:29, 11 July 2012 (UTC)

I am not complaining about anything ;-) just defending the original statement in this article. I am equally shocked and worried that the rate of human energy consumption is already 1/6 of the global rate of photosynthetic energy capture. I guess this should not be too terribly surprising since at the rate we are going, we will have burned in a few hundred years all the fossil fuels on earth that took millions of years of plant growth to create. Boghog (talk) 12:09, 11 July 2012 (UTC)

P.S: I appreciate your feedback :-). Boghog (talk) 18:50, 11 July 2012 (UTC)

Hey man, de nada! I appreciate your appreciation! Cheers, JonRichfield (talk) 19:58, 11 July 2012 (UTC)

in the article it states that 100 thousand million watts is 100 terawatts. 100 terawatts is 100 million million watts not 100 thousand million watts. 100,000,000,000,000 is 100 trillion as the standard counting system goes: thousand, million, billion, trillion. these numbers change as they become prefixes to messurement, they become: kilo, mega, giga, tera. i believe that i am correct in saying that the estimate for photosynthesising power is 100 thousand BILLION watts as a posed to 100 thousand Million watts. please correct me if i'm wrong — Preceding unsigned comment added by 2.27.71.134 (talk) 14:57, 6 January 2013 (UTC) 2.27.71.134 (talk) 15:13, 6 January 2013 (UTC)Thor Preston another thing to think about when calculating averages for photosynthesising power is that most of the earth is sea which consists of significantly fewer photosynthesising organism per surface area. add to this areas sush as deserts (including Antarctica) where there is no plant life anyway, and areas forested with deciduous trees and it doesn't seem suprising that only 0.1% of solar enerry is used i photosynisis. i believe that this figure is reasonably accurate (as far as making such estimates is concerned) 2.27.71.134 (talk) 15:13, 6 January 2013 (UTC)Thor Preston

Power vs. Energy

Looking at the history of this article and its talk page, I see that some folks have a bit of trouble with terms like megawatts vs megawatt hours vs. megawatts per hour. Others, of course, understand the basic concepts, get it right every time, and are faced with others being confused. I am going to try to bring everyone up to speed.

First, consider units. You can measure a distance with meters, kilometers, feet, or miles, and you can easily convert between these units, because they are all units of distance.

You can convert miles per hour into meters per second or convert feet per second into kilometers per hour because they are all units of speed.

You cannot convert miles into kilometers per hour or feet per second into meters. That's because one is distance and the other is speed. Kilometers are kilometers - no time is involved. Kilometers per hour involve a unit of time.

One important detail is that kilometers per hour is an instantaneous measurement - 100 kilometers per hour means that you are going 100 kilometers per hour at this instant in time. Going 100 kilometers per hour for an hour gives you a distance -- 100 kilometers -- thus cancelling out the "hour" in kilometers per hour. Photosynthesis is a very important process in biology and its very complicated

Here is where our terms for describing energy and power get confusing. There is no such thing as watts per hour or watts/hour, only watt hours, which are not the same thing. Other measures of power are described per unit of time (calories per second, for example) and therefore it would seem logical that a kilowatt hour would be a unit of power. Logical, but wrong.

The problem is that a watt is one joule per second. It's as if someone decided to get rid of kilometers per hour and used the term "clicks" instead. But if clicks are defined as kilometers per hour, how would we describe a kilometer using the "click" term? We would have to come up with something like "click hours" to describe kilometers. And, of course, half the people would think a "click" is a kilometer and that "clicks per hour" or "clicks/hour" (kilometers per hour per hour) has meaning.

So as a quick cheat sheet, just remember the following:

Power is like speed. Watts are like miles per hour -- a car is going 100 kilometers per hour at one particular moment, and a light bulb is consuming 100 watts at one particular moment.

Energy is like distance. Watt hours are like kilometers. You can think of a kilometer as "how far a person walking at one kilometer per hour goes in one hour", but hours have nothing to do with kilometers. The "how far..." statement above simply means that you are canceling out the "hour" in "kilometers per hour."

Likewise, you can think of a 3600 watt hours as "how much energy a space heater consuming 3600 watts (3600 joules per second) of power consumes in one hour", thus cancelling out the "seconds" in "joules per second" (3600 seconds = 1 hour).

A basic rule of the Internet is that every technical explanation contains one or more stupid errors or typos that make it wrong, so you can beat me up over my errors here (smile). --Guy Macon (talk) 14:52, 25 July 2012 (UTC)

There is of course a third class of individuals who many years ago aced undergraduate physics courses but since then have spent most of their time in chemistry and work with kJ/mol on a daily basis and momentarily forgot that watt = joule/second ;-) Boghog (talk) 20:23, 25 July 2012 (UTC)

"...six times larger than the power consumption of human civilization..."

I am trying to verify the following statement in this article:

"The average rate of energy capture by photosynthesis globally is immense, approximately 130 terawatts,[2][3][4] which is about six times larger than the power consumption of human civilization.[5]"

From the Food and Agriculture Organization of the United Nations, Renewable biological systems for alternative sustainable energy production (FAO Agricultural Services Bulletin - 128) [ http://www.fao.org/docrep/w7241e/w7241e05.htm ]:

"Approximately 114 kilocalories of free energy are stored in plant biomass for every mole of CO2 fixed during photosynthesis. Solar radiation striking the earth on an annual basis is equivalent to 178,000 terawatts, i.e. 15,000 times that of current global energy consumption. Although photosynthetic energy capture is estimated to be ten times that of global annual energy consumption, only a small part of this solar radiation is used for photosynthesis.

"[T]he theoretical maximum efficiency of solar energy conversion is approximately 11%. In practice, however, the magnitude of photosynthetic efficiency observed in the field, is further decreased by factors such as poor absorption of sunlight due to its reflection, respiration requirements of photosynthesis and the need for optimal solar radiation levels. The net result being an overall photosynthetic efficiency of between 3 and 6% of total solar radiation."

On the other hand, from [ http://rsta.royalsocietypublishing.org/content/365/1853/1007.full ] I get:

"The Sun provides solar energy to our planet on an annual basis at an average rate of 100,000 TW, exceeding our current rate of demand of approximately 14 TW a year by 7000 times."

"Overall, an approximate efficiency of global photosynthesis is 0.2%."

So I am getting a wide variation in estimates from reliable sources, which usually means that the article should give a range of estimates.

If anyone has access to the sources we currently cite for the statement in question, would you be so kind as to post an exact quote where the source says what we say it says? --Guy Macon (talk) 15:55, 25 July 2012 (UTC)

I don't have such sources, but I share your discomfort at what strikes me as some very doubtful estimates within what seem to me very wide fiducial limits. I think that some serious rewording would be in order. JonRichfield (talk) 17:42, 25 July 2012 (UTC)

To state the obvious, the vast majority of light energy that strikes the earth is not absorbed by plants. If this is not the case, please explain to me why this picture isn't mostly green? Furthermore, the efficiency of photosynthetic energy capture is completely irrelevant to the estimates of global photosynthetic energy capture that is based solely on atmospheric oxygen isotopic ratios. If you compare apples to oranges, you get numbers that are all over the place. If you compare apples to apples, the estimates are very consistent. Boghog (talk) 19:59, 25 July 2012 (UTC)

Comparing apples to apples: "about six times larger than the power consumption of human civilization" ≈ "photosynthetic energy capture is estimated to be ten times that of global annual energy consumption". The statement that "only a small part of this solar radiation is used for photosynthesis" is also true and in no way contradicts the previous statement. Q.E.D. Boghog (talk) 20:12, 25 July 2012 (UTC)

I am not so much concerned with us getting this totally wrong -- clearly we are in the ballpark -- but rather with unwarranted precision. when the first two places I looked had figures of 0.2% and 6% for one part of the equation, that's a 30 to 1 difference. Off the top of my head I would guess at least a 2 to 1 difference in estimates of how much of the sun gets intercepted by plants and some smaller percentage for how much sunlight hits the earth, It looks like our estimates could be an order of magnitude too large or too small. I think we need to rewrite this part of the article to give a range of estimates. --Guy Macon (talk) 22:58, 25 July 2012 (UTC)

The 130 terawatts estimate of the rate of global photosynthetic energy capture is not dependent on estimates of how much of the sun gets intercepted by plants nor on estimates of how much sunlight hits the earth. The estimates are based on ratios of oxygen isotopes in the atmosphere which are perturbed by photosynthesis. The more photosynthesis, the greater the perturbation. From this perturbation, one can estimate the amount of carbon fixed by photosynthesis. This in turn can be converted into a rate of energy capture (for more details about how this estimate was arrived at, see the comment in reference #3, Whitmarsh and Govindjee, 1999). Atmospheric oxygen isotope ratios can be measured quite accurately (although the interpretation is somewhat tricky, see PMID 21956330) and hence estimates of the rate of global photosynthetic energy capture are also reasonably accurate. Boghog (talk) 06:20, 26 July 2012 (UTC)

Ah. That makes sense. Do you think that method supports a much smaller range of figures than I got above with another method, or do you think it supports an exact figure? --Guy Macon (talk) 06:51, 26 July 2012 (UTC)

Yes, I think the method does support a smaller range of figures probably well within a factor of two. While the precision of the estimate using this method is very high, the accuracy is some what lower because of uncertainties introduced by several of the underlying assumptions (again see Welp, et al., PMID 21956330). Based on Welp, et al., the estimate probably should be revised upwards to ~160 TW. However Welp, et al. do not directly report the rate of global photosynthetic energy capture, only estimates the amount of carbon fixed by photosynthesis and I did not want to be accused of original research (although per WP:CALC, reporting the revised estimate may be justified). Boghog (talk) 07:40, 26 July 2012 (UTC)

Sorry for not responding to this earlier: "would you be so kind as to post an exact quote where the source says what we say it says?". Following the links already in this article provide exact quotes:

• reference #2: link to full article: Table 1. Sources of energy on earth, energy used for photosynthesis: 100 TW, yearly budget, ambiguous and sloppy, but accurate if "yearly budget" is interpreted as an average rate of energy capture over one year. No range given. All the numbers in this table are order of magnitude estimates and rounded to the nearest 100. I admit because of the ambiguity in the source, this source is not ideal.
• reference #3: link to transcribed version of full article, section #8, "This is equivalent to 4 x 10¹⁸ kJ of free energy stored in reduced carbon" (again no range given) which is equivalent to 127 TW.
• reference #4: link to google book preview, "The average global rate of photosynthesis is 130 TW (1 TW = 1 terawatt = 10¹² watt)." No range given.

In summary, none of the original sources provide ranges which implies but of course doesn't prove the estimates are accurate to within the accuracy of the numbers that are reported. Boghog (talk) 17:59, 26 July 2012 (UTC)

Edit request on 23 August 2012

Please, change the photosynthetic reaction from 6CO2+6H2O -----> C6H12O6 + 6O2 to 6CO2+ 12H2O -----> C6H12O6 + 6O2 + 6H2o since in the reaction the water molecule could be cancelled but by the research it has shown that it produces 6 molecule of water. Rasish150 (talk) 13:23, 23 August 2012 (UTC)

Declined. You need to show a reliable source. Furthermore even if a reliable source demonstrated that six moles of water are produced, it is still customary to write chemical reactions as the net change of reactants and produces where any "extra" molecules that appear on both sides of the reaction are cancelled. Boghog (talk) 20:48, 23 August 2012 (UTC)

This topic is revisited at #Factor of 2 in photosynthesis equation. -- ToE 14:28, 4 February 2015 (UTC)

Superposition of states in photosythesis

"Quantum Secrets of Photosynthesis Revealed": http://www.lbl.gov/Science-Articles/Archive/PBD-quantum-secrets.html - I believe, it's worth to mention — Preceding unsigned comment added by 79.185.123.97 (talk) 14:23, 10 November 2012 (UTC)

Old vandalism

The article seems to have been a victim of severe vandalism in 2009. I accidentally found out that some of it survived into 2013. In October 2009, an anonymous user replaced the name of Gabrielle Matthaei with the name of Albert Einstein. I only know the basics of photosynthesis itself, so I suggest that someone checks the article thoroughly for more mistakes. This one was rather serious. Surtsicna (talk) 00:13, 3 January 2013 (UTC)

Article should mention use of halorhodopsin or bacteriorhodopsin for photosynthesis instead of chlorophyll

Somewhere this article should mention that halobacteria use a different method of photosynthesis not based on chlorophyll. See Photosynthesis - Halobacterium. See also Archaearhodopsin and Halorhodopsin and haloarchaea

I've just added a para about this to the overview. Summarized it briefly - that it is a probably separately evolved method of photosynthesis closely related to vision, that doesn't involve carbon capture or production of oxygen. I'm not knowledgeable in this area - so please, if anyone here knows more about it, I think the article needs a separate section about it. Though this article is quite technical, I'm pretty sure it doesn't mention this anywhere else. If it does, it should be signposted more clearly. Robert Walker (talk) 14:43, 31 August 2014 (UTC)

Contradiction in Efficiency section ? two ranges

"Plants usually convert light into chemical energy with a photosynthetic efficiency of 3–6%."

"Actual plants' photosynthetic efficiency varies with the frequency of the light being converted, light intensity, temperature and proportion of carbon dioxide in the atmosphere, and can vary from 0.1% to 8%"

Well which is it? 3-6% or .1% to 8%? Be consistent, don't throw two ranges, especially with one line following the other. ScienceApe (talk) 18:24, 11 October 2014 (UTC)

There is no contradiction. The two estimates come from two different sources but are compatible with each other. The maximum range is 0.1–8% while a more typical range is 3–6%. The later range falls within the former. At worst, mentioning the two estimates is redundant. Perhaps the first sentence should be merged into the second, something like "... and can vary between 0.1–8%^[32] but more typically between 3–6%.^[34] Boghog (talk) 18:54, 11 October 2014 (UTC)

Two estimates with different ranges do indeed contradict each other especially when they vary so drastically. Keep it to one estimate, use whatever source is more reliable. ScienceApe (talk) 23:52, 11 October 2014 (UTC)

I don't think that the current content is contradictory as the efficiency varies wildly depending on the species and the environment. The sources are poor though and there must be better ones available somewhere. SmartSE (talk) 00:22, 12 October 2014 (UTC)

Well that's why you have a range of efficiencies. One range takes into account those factors. Two ranges contradict each other. ScienceApe (talk) 01:42, 13 October 2014 (UTC)

If the ranges did not overlap, then they would contradict each other. However one range is entirely within the other. Both of the quoted ranges correspond to a fraction of a continuous probability distribution, the broader range captures higher percentage of the variation in photosynthetic efficiencies (the including extremes) where as the narrower range captures only the more typical values. It depends on what you are more interested in knowing. As already made clear in the article, the 3–6% range corresponds to the "usual" values and the 0.1– 8% range to the extreme values. Both estimates are useful. Boghog (talk) 10:00, 13 October 2014 (UTC)

I don't agree, if you have two different ranges, then that's a contradiction. In any case, I think we are chasing a red herring here. Having two ranges is redundant if nothing else, have one range, not two. ScienceApe (talk) 00:45, 15 October 2014 (UTC)

No contradiction. First range is "usual" including some proportion of cases. The 2nd is the limits of all cases. Both are useful, to different readers. - Rod57 (talk) 12:08, 16 February 2021 (UTC)

Factor of 2 in photosynthesis equation

The article currently gives the following equations:

2n CO₂ + 2n DH₂ + photons → 2(CH₂O)_n + 2n DO (General equation)

2n CO₂ + 4n H₂O + photons → 2(CH₂O)_n + 2n O₂ + 2n H₂O (Oxygenic photosynthesis)

2n CO₂ + 2n H₂O + photons → 2(CH₂O)_n + 2n O₂ (Oxygenic photosynthesis, simplified)

What is the purpose of carrying the extra factor of 2? Why not simply write the following?

n CO₂ + n H₂O + photons → (CH₂O)_n + n O₂

Is there something inherently two by two in photosynthesis?

I asked this question on the Science Reference Desk here, but didn't find resolution. One answerer suggested that it might be because "the reactions involved are Lewis acid-base reactions, which depend on the transfer of electron pairs", but another answerer questioned this and said that they were used to seeing the general formula without the doubling. -- ToE 15:30, 29 January 2015 (UTC)

The chemical equations look to be the products of random vandalism. I restored these equations to an earlier version that made more sense. Boghog (talk) 17:01, 29 January 2015 (UTC)

This article sure does have a long edit history, and a lot of that is vandalism, but I don't think that is the source of the "2"s. Looking through the history a bit more I see that not only does the factor of 2 go a long way back, but it comes from not assuming that the "D" and "O" combine in the first formula. Back in 2009 it looked something like:

2n CO₂ + 2n DH₂ + photons → 2(CH₂O)_n + 2n D + n O₂

where the 2 is necessary. Setting D to O gives:

2n CO₂ + 2n H₂O + photons → 2(CH₂O)_n + 2n O₂

unless you cancel the factor of 2 at the same time.

Is there any problem with our use of "DO" in the first equation? -- ToE 23:37, 29 January 2015 (UTC)

Good observation. D = electron donor, A = electron acceptor, O = oxygen atom. The more generic equation used D, the more specific equation uses O. In principle, "DO" could form in which case multiplying the equation by two is not necessary. If D₂ and O₂ instead form, then multiplication by two is necessary in the general equation. It is not necessary in the more specific equation. Just as in mathematics, it is common practice to divide both sides of the equation so that the smallest integer coefficients are displayed (2x = 2y → x = y). An exception is made if an integer multiple represents to a specific reactant or product. For example, hexoses such as glucose are the most frequent products of photosynthesis in which case it make sense to write the following equation:

• 6CO₂ + 12H₂O + light energy → C₆H₁₂O₆ + 6O₂ + 6H₂O

or more simply:

• 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

I question if we need to include the general reaction since it is not very commonly used by photosynthetic organisms. The general equation is very abstract and it would be good to see some specific examples. I need to look into this further. More later. Boghog (talk) 08:32, 30 January 2015 (UTC)

Is it strange that the 2009 version using "A" considered Oxygen an electron acceptor while the current one uses "D" and considers it an electron donor? Is this because it is really the complete compound, water, which is the electron donor, with 2 H₂O -> 2 e^- + 2 H⁺ + O₂, and the "D" in the current version isn't so much saying that Oxygen is an electron donor as it is saying that "D" is the part of the compound DH₂, with that compound acting as the electron donor, while the "A" in the 2009 version is instead saying that while it is part of an electron donor compound, its role in forming that compound is as an electron acceptor, such as with Oxygen in the formation of Water 2 H₂ + O₂ = 2 H₂O? We seek reliable sources for our facts; perhaps we need to survey some textbooks to see how this is typically presented. (Although I wouldn't be surprised if it is presented differently by different authors.) -- ToE 13:14, 30 January 2015 (UTC)

Yes, I also noticed different versions used "A" or "D". Oxygen is an oxidizing agent, acts as an acceptor, while water acts as a donor. As you suggest, we need to do some more reading to see how this is usually presented. More later. Boghog (talk) 13:28, 30 January 2015 (UTC)

After digging around a bit, it appears that the generalized photosynthetic reaction as first proposed by Cornelius van Niel is usually written as:

• CO₂ + 2H₂A + Light Energy → [CH₂O] + 2A + H₂O
• Singhal GS, Renger G, Sopory SK, Irrgang KD, Govindjee, ed. (1999). "Chapter 2: The Basic Photosynthetic Process". Concepts in Photobiology: Photosynthesis and Photomorphogenesis. Boston: Kluwer Academic Publishers. p. 13. ISBN 978-0792355199. {{cite book}}: External link in |chapterurl= (help); Unknown parameter |authors= ignored (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help)CS1 maint: multiple names: editors list (link)

There is no need to combine A (or D) with O. I have modified the text accordingly. Does this look OK? Boghog (talk) 09:59, 31 January 2015 (UTC)

It's balanced and it's sourced, so that's great. Thanks. You also included in the article what Whitmarsh and Govindjee call "The empirical equation representing the net reaction of photosynthesis for oxygen evolving organisms":

• CO₂ + 2H₂O + Light Energy → [CH₂O] + O₂ + H₂O

which is good, but I am confused by why a "net" reaction wouldn't cancel an H2O from each side:

• CO₂ + H₂O + Light Energy → [CH₂O] + O₂

I'll try to read some more on the subject. -- ToE 20:21, 31 January 2015 (UTC)

You are right that a net reaction would cancel the extra mole of water that appears on both sides of the reaction equation. I have looked at several other sources, and some cancel the extra water while others leave it in. I think the reason that it is often included is to make clear that water is both a reactant (in the light-dependent reaction) and a product (in the light-independent reaction). The present version of the text uses the word "general" instead of "net" thus avoiding this semantic issue. Boghog (talk) 20:51, 31 January 2015 (UTC)

That is exceedingly well phrased -- that it is "to make clear that water is both a reactant (in the light-dependent reaction) and a product (in the light-independent reaction)" -- and I think that something like that should go in the article. I don't know whether or not we should include the net reaction in the article (I lean slightly in favor of doing so), but the having the general equation (with water on both sides) without explanation would seem confusing to readers who have an understanding of chemical equations but who haven't grasped that the equation is for a process which is composed of multiple reactions.

Back to Whitmarsh and Govindjee, it strikes me as a bit incongruous for them to provide the empirical equation (with water on either side) immediately following the statement, "By the middle of the nineteenth century the key features of plant photosynthesis were known, namely that plants could use light energy to make carbohydrates from CO2 and water." They don't explicitly say that they equation they provided would have been used at that time, but it would be easy to infer that. I assume that it wasn't until much later, when the overall process was better understood, that such an equation would have been expressed. -- ToE 17:48, 2 February 2015 (UTC)

I just meekly made the change I suggested above. If it's too wordy I sure someone will trim it (or remove it outright). In any case, thanks a lot Boghog! -- ToE 18:14, 2 February 2015 (UTC)

And I just noticed that this topic is related to #Edit request on 23 August 2012. -- ToE 14:30, 4 February 2015 (UTC)

The net equation above is correct, but the net equation given in the article still has 2 mole H2O on the left side- it's unbalanced. A simple mistake to fix: someone please take the 2 out in the article.--94.5.3.63 (talk) 11:29, 23 December 2015 (UTC)

Which equation are you referring to? The following in the overview section:

• CO₂ + 2 H₂O + photons → CH₂O + O₂

or the following equation in the light dependent reactions section:

• 2 H₂O + 2 NADP⁺ + 3 ADP + 3 P_i + light → 2 NADPH + 2 H⁺ + 3 ATP + O₂

Both look balanced to me. It takes two moles of water to produce one mole of molecular oxygen. Boghog (talk) 12:25, 23 December 2015 (UTC)

The image Calvin-cycle4.svg is incorrect?

There seems to be an error in the Calvin Cycle image. The image indicates that 3-phosphoglicerate would be the product that is taken out of Calvin Cycle. However, the article says that the product is Glyceraldehyde 3-phosphate (G3P or GAP). The sources I have found also tell the same.

I posted this question earlier at Talk:Light-independent reactions, so let's discuss it there. --PauliKL (talk) 09:40, 12 October 2015 (UTC)

Hydrogen

I find the following statement that was added in this edit problematic: freeing hydrogen for use within the plant. This give the impression that hydrogen produced in what ever form has a significant half-life in plants. This is very misleading. According to Stryer:

2Q + 2H₂O + Light → O₂ + 2QH₂

where Q represents plastoquinone and QH₂ represents plastoquinol. Hence hydrogen is not generated even as an intermediate, rather hydrogen derived from water is directly transfer to plastoquinone. Boghog (talk) 21:18, 23 November 2015 (UTC)

References

I guess this dispute might be related the old problem of element names having multiple meanings. Hydrogen to chemists and biochemists means H₂, which, like you said is not involved at all in photosynthesis (it would be a big deal if it did). Hydrogen to a nonscientist might, I guess, mean H+, in which case our oceans are full of hydrogen, which has no reducing power in the absence of photosynthesis. Sometimes, biochemists will write H2 meaning that the equivalent of H2 is delivered, but in all cases (except one step in one variant of methanogenesis) such "hydrogen" always comes in the form of H+ and e-. Chlamydomonas reinhardtii does couple H2 production to photosynthesis, but the former reaction involves a hydrogenase, uniquely qualified in nature to interact with H2. --Smokefoot (talk) 23:09, 23 November 2015 (UTC)

Semi-protected edit request on 24 February 2016

The reaction

CO2 + 2 H2O + photons → CH2O + O2

is wrong. It doesn't balance. It should be

CO2 + H2O + photons → CH2O + O2

See the original wikipedia web page for subscripts.

92.192.9.39 (talk) 17:53, 26 November 2015 (UTC) Robert L. Baber, http://office.rlbaber.de

I think that the equation after "but canceling n water molecules from each side gives the net equation" is a bit off. The left hand side should have only one H2O molecule, i.e.:

CO2 + H2O + photons → CH2O + O2

instead of

CO2 + 2 H2O + photons → CH2O + O2 72.20.109.118 (talk) 06:54, 24 February 2016 (UTC)

 Fixed Thanks for the heads up. Yes, that is a typo which I have fixed. I have also removed n from all the equations for consistency and simplicity. Cheers. Boghog (talk) 08:56, 24 February 2016 (UTC)

Semi-protected edit request on 25 May 2016

The third sentence in the second paragraph in the Overview section should probably be "The addition of electrons to a chemical species is called a reduction reaction" rather than "The addition of an electrons to a chemical species is called a reduction reaction" Pchisarik (talk) 13:33, 25 May 2016 (UTC)

 Fixed thanks. Sir Joseph ^(talk) 13:57, 25 May 2016 (UTC)

equations are not correct

For the light-dependent reactions we have the following:

2 H₂O + 2 NADP⁺ + 3 ADP + 3 P_i + light → 2 NADPH + 2 H⁺ + 3 ATP + O₂

This is not correct. When ADP + Pi condensate to ATP water is produced. ADP = C₁₀H₁₅N₅O₁₀P₂ and Pi (inorganic phosphate) = H₂PO₄ whereas ATP = C₁₀H₁₆N₅O₁₃P₃. So count the oxygens and the hydrogens and you will clearly see that water is missing (or other way round: for the hydrolysis of ATP you need water that is why it is called hydrolysis, but for unknown reason missing).

Hence, in the above formula 3 H2O needs to be added to the right side.

Same is the case for the Calvin cycle formula: 3 CO₂ + 9 ATP + 6 NADPH + 6 H⁺ → C₃H₆O₃-phosphate + 9 ADP + 8 P_i + 6 NADP⁺ + 3 H₂O. Here, water is missing on the left side. --155.91.64.15 (talk) 11:03, 31 May 2017 (UTC)

Thank you 155.91.64.15. I've just gone through a few textbooks to make sure I've not missed something obvious. I believe that you are correct. MBOC and Biochemistry, just state the equation without specifying the number of water molecules (I suspect for just this reason). I'm going to bring this up on the WP:MCB discussion page to work out the best way to write the corrected equations (and get a second opinion). T.Shafee(Evo&Evo)^talk 12:21, 17 September 2017 (UTC)

References

Typo

The word "Phototorespiration" is inside the text. A mere typo of "photorespiration". I would fix it myself but the article is protected.

Thanks for the heads up! I've left a message for you on your talk page. – Rhinopias (talk) 16:44, 27 September 2017 (UTC)

Semi-protected edit request on 8 December 2017

In the Efficiency Section there is a grammatical structure error. The third sentence is not a complete sentence. Currently it reads "A fact that allows measurement of the light reaction of photosynthesis by using chlorophyll fluorometers.[35]"

Better structure is "This fact allows measurement of the light reaction of photosynthesis by using chlorophyll fluorometers.[35]" Rudyhehn (talk) 16:00, 8 December 2017 (UTC)

Done DRAGON BOOSTER ★ 17:21, 8 December 2017 (UTC)

Carbon fixation in the Overview section

In the Overview section, the following sentence appeared: "Photosynthesis provides the energy in the form of free electrons that are used to split carbon from carbon dioxide that is then used to fix that carbon once again as carbohydrate". I cannot really match that to the description of the Calvin cycle below, where it seems to be energy in the form of ATP and NADPH that does the work. In the problematic sentence, the "that" I think refers to the "carbon dioxide"; but the Calvin-cycle section does not describe carbon dioxide as fixing a split-off carbon. (Besides that, it should be a non-defining relative clause: "from carbon dioxide, which is then used".) So this sentence appears to need some editing. A very simple alternative would be "...; photosynthesis provides the energy to convert carbon dioxide in the air into carbohydrates". Perhaps that is all that is required here.

I would have been bold and made the change, but then the next sentence also had me confused: "Carbon fixation is an endothermic redox reaction, so photosynthesis supplies the energy that drives both process". What is the second process? (And, of course, grammatically it should read "processes"!)

Please could someone with more knowledge of biochemistry help here. Jmchutchinson (talk) 17:17, 20 January 2018 (UTC)

Thanks for the heads up. I agree that the sentence needs some work. Photosynthesis does not split carbon from carbon dioxide, but rather it reduces carbon dioxide to produce sugars. Also the "free electrons" produced by photosynthesis are in the form of the reducing agent NADPH. I think your proposed sentence:

• photosynthesis provides the captures energy from sun light to convert carbon dioxide in the air into carbohydrates

is definitely an improvement, but I would strike in the air, since aquatic plants use carbon dioxide dissolved in water as a carbon source. Also would change "provides" into "capture". The sun provides the energy, chlorophyl captures it. Does this sound reasonable? Boghog (talk) 20:52, 20 January 2018 (UTC)

• Thanks, excellent suggestions. I have now edited the text accordingly. For the sentence following, I simply deleted the problematic second half as it was unnecessary repetition now. Jmchutchinson (talk) 21:44, 20 January 2018 (UTC)

Semi-protected edit request on 1 July 2018

At the beginning of paragraph three under heading "Overview", in the line ending with citation 14, my grandfather's name is misspelled. It should read "Cornelis van Niel," not Cornelius. Thank you for correcting this error. Enwent (talk) 04:39, 1 July 2018 (UTC)

 Done. Thanks for the clear request, Enwent. Adrian J. Hunter^{(talk•contribs)} 04:56, 1 July 2018 (UTC)

Net equation is wrong

CO₂carbon
dioxide + H₂O water + photonslight energy → [CH₂O]carbohydrate + O₂ oxygen

This is wrong as it gives the idea that part of the oxygen generated comes from the carbon dioxide whereas that's not true. Radiotyping oxygen has shown that all generated oxygen comes from the water. So two water molecules are consumed and one is produced. You cannot cancel in stoichiometric equation it's not mathematics.Linkato1 (talk) 14:52, 14 December 2018 (UTC)

Net equation is correct because,you have to first note that to get corbon dioxide, we add corbon and oxygen, so know that corbon dioxide, also called CO2 is found in water as a dissolved gas. It can dissolve in water 200times more easily than oxygen ( so note that even water contains corbon dioxide much more than oxygen. Murangira fagiesoja (talk) 21:19, 26 November 2020 (UTC)

Semi-protected edit request on 16 April 2020

Hi.plz can you make this make sense.it does not make sense to me.can you make it so that everyone can understand it(even kids).thanks 2A02:C7F:9A5A:AD00:CCED:3356:A1B4:D41E (talk) 11:19, 16 April 2020 (UTC)

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. You might also want to try the Simple English Wikipedia article on this subject at simple:Photosynthesis. —KuyaBriBri^Talk 14:34, 16 April 2020 (UTC)

Photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds photosynthesis important because It's not oxygen production. The primary function of photosynthesis is to convert solar energy into chemical energy and then store that chemical energy for future use. For the most part, the planet's living systems are powered by this process — Preceding unsigned comment added by Fazepress (talk • contribs) 06:22, 8 October 2020 (UTC)

C4/C3 efficiency

Looking for a single figure I found "C4 species such as maize, sorghum, and sugarcane have 50% higher [radiation use efficiency] RUEs than those of C3 crops such as rice, wheat, and potato (Kiniry et al., 1989; Sage, 2004)."Strategies for engineering a two-celled C4 photosynthetic pathway into rice, 2011. Could use in an intro to the C3 : C4 section ? - Rod57 (talk) 12:02, 16 February 2021 (UTC)

Semi-protected edit request on 13 July 2021

Please rename the "Discovery" section to "History of Research" or something similar, since the section covers not only its discovery but its history as late as 1963. 72.77.42.118 (talk) 12:09, 13 July 2021 (UTC)

 Not done for now: please establish a consensus for this alteration before using the {{edit semi-protected}} template. Thank you very much for your idea! There are still parts of this amazing process that we don't understand very well, so it might be said that the "discovery" is an ongoing process that began long ago. Scientists discover new details equably, so yes, there is a "history" involved, and that history is all about the ongoing discovery of this detail and that detail of the photosynthesis process. Thanks again! P.I. Ellsworth  ed. ^put'r there 20:37, 13 July 2021 (UTC)

Paine Ellsworth, thanks for answering this edit request. I've been trying to think of a good way to explain why I was going to close it, but you did it more succinctly and downright nicely than I would have. ScottishFinnishRadish (talk) 20:41, 13 July 2021 (UTC)

You're very welcome, editor ScottishFinnishRadish! and thank you so much for your kind words! We try to be understanding and helpful to other editors, especially new editors and IP editors (potentially registered). Not always successful and sometimes misunderstood, but that's the nature of the beast, I guess. And we hope you also keep up the good and helpful work! PS – have you seen this essay? Reckon some of us do our best to shatter its premise?! P.I. Ellsworth  ed. ^put'r there 21:04, 13 July 2021 (UTC)

How about "Experimental history" then? I have to say the IP-user has a point: the term 'discovery' will mean different things to different people (it made me think of the lollipop-flask experiments by which the dark part, the Calvin cycle, was discovered, and I didn't think at all about the initial process of discovering that plants fix CO2, or about the light-stage; that is my bias). A more neutral and inclusive term would fit the content rather well.

On another matter altogether, I notice the article doesn't have anything on C3/C4 intermediates (e.g. Moricandia)? Are they relevant? Elemimele (talk) 21:26, 13 July 2021 (UTC)

I see "discovery" as the first time someone found out about the process, when a scientist first demonstrated the basic idea that plants use light to generate energy. ("Discovery" might be a subsection that ends just above the appearance of Cornelis Van Niel.) Everything after that is a refinement of the basic idea, as more details are discovered and our knowledge about the process is refined. I think "Experimental history" is better because it doesn't have confusing alternate meanings like "Discovery" does. If we all agreed that it would fit the content all right, I think we should use it. 72.77.42.118 (talk) 14:36, 14 July 2021 (UTC)

Okay and  done, and to editor Elemimele, not sure what you mean by C3/C4 intermediates. We see in that same section the paragraphs on C3 : C4 photosynthesis research, but we don't see Moricandia specifically used. Is that similar? P.I. Ellsworth  ed. ^put'r there 21:04, 14 July 2021 (UTC)

Hi @Paine Ellsworth:, here's some blurb with a few articles that describe C3/C4 intermediates [[1]]; Google will produce others. They have Kranz anatomy with bundle-sheath cells but they lack most of the enzymatic stuff of C4, and as the name suggests, achieve compensation points/behaviour somewhere between C3 and C4. I don't know if they're too much of a niche subject. I can't judge: I once, a long time ago, worked in a group that had an interest in them, so I'm biased (COI!), but I have no direct expertise in the area. Elemimele (talk) 21:34, 14 July 2021 (UTC)

Science

What is photosynthesis what does it neans 119.235.54.94 (talk) 13:21, 29 December 2021 (UTC)