Talk:C4 carbon fixation

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This article isn't as good as it could be. I'm gonna try a basic rewrite. I got pretty far now, but I'm tired. I'll come back later and finish if no one else does in the meantime. This is an important adaptive strategy, and the quality of the article should reflect it! GuildNavigator84 12:05, 22 May 2006 (UTC)


The cuurent article states, "But since otherwise tropical plants lose more than half of photosynthetic carbon in photorespiration, the C4 pathway is an adaptive mechanism for minimizing the loss." Does anyone have a citation for this? Often 25% is used as a hand-waving average number. Falkowski and Raven's book state, "In terrestrial C3 plants, which rely purely on diffusive CO2 suuply to Rubisco, photorespiratory consumption of O2 can easily be 25% of the activity of the enzyme in vivo (see Raven 1984)." 16:35, 30 June 2006 (UTC)

Yes. As far as I understand it: in a few experiments, photorespiration has resulted in the loss of up to 50% of fixed carbon. However, this was not the norm, as that sentence suggests. I think that 30% loss is above average, and is considered a bad day. The losses are significant, however, and cut two ways-- every time you photorespirate, you miss out on that opportunity for photosynthesis, so there's an opportunity cost of carbon fixation. However, there is also the additional cost that you have to use previously fixed carbon products to undo the results of the photorespiration, which makes it even worse. Gcolive 03:29, 1 August 2006 (UTC)

Hey, I am not sure if this qulifies as a source, but here is mention of seperate evolution of c-4 page 13 (talk) 09:18, 12 February 2008 (UTC)

I don't know whether to add it based on the "better than nothing" theory, but it would perhaps be better to cite the Simon Conway Morris book (if he mentions the C4 example, that is). This one doesn't go into much detail (for example, what are the 31 lines they mention), or subleties (how many genes need to change to switch C3 to C4? How much has the biochemistry of a random species been studied?), or cites which could lead to further digging. Summary: fine to add it if you want, as far as I'm concerned. Kingdon (talk) 21:52, 12 February 2008 (UTC)

Formatting of "C4"[edit]

I came here to find out whether it was C4 or C4 plants. This article is inconsistent with itself. I added a contradiction tag. - (talk) 04:23, 30 March 2008 (UTC)

Don't know if that is the right tag for typography issues, but anyway C4 (uppercase, not lowercase, C) seems to be right. At least, all the top hits in a google search for "C4 carbon fixation" used the subscript: [1] [2] [3] [4] [5] [6] [7]. Having said that, I'm not sure it is worth expecting 100% consistency (for example, as far as I know there is no technical way to put a subscript into the title of the wikipedia article, and some of those other sites seem to have similar constraints). If someone has better information on whether C4 is in fact preferred (for example, if there is some style guide or something to consult), do speak up. Kingdon (talk) 06:27, 30 March 2008 (UTC)

Some Simple Examples Please[edit]

So, until today, C4 meant, to me, a kind of plastic explosive. So here I'm reading that there's two kinds of carbon plants, no, three. There's C4 plants and the more primitive C3 plants. And something else.

OK, so take a four-leaf clover. Which is it, C3 or C4? An oak tree? Marigolds? Algae?

The article talks about some obscure latin-named stuff from "in the deserts of south-east Asia" that does an odd variant of C4. Cool. Well I thought southeast asia was all pretty humid, that's the way it was when I visited. But whatever. How about regular-old C4? Do pine trees do it? Venus Fly Traps? Carrot plants?

My guess is that either C4 is dominant or C3 is dominant, and the other is like really obscure and only happens in places like the 'deserts of the amazon' or 'the jungles of antarctica'. or something. Like how all living things we see around us, plants and animals, are eukariots, prokariots are obscure. So that's what I'd like someone to explain, what plants do C3 and what does C4. In the opening paragraphs, please: why should we care about the difference between C3/4. Thanks! (talk) 23:58, 2 February 2009 (UTC)

Thanks for pointing that out, I've added a few examples. In answer to your other questions most plants are C3 (carrots, oak trees etc.). Neither c4 or CAM plants are obscure exactly (it depends a lot on where you live). All algae are C3 - they're far too small to have spatial seperation of co2 uptake and use. Some bacteria have carboxysomes which perform a similar function to C4. On another note I'd hardly say that prokaryotes are obscure - there are more prokaryotic cells in you than eukaryotic ones! (see Gut flora). Smartse (talk) 17:08, 3 May 2009 (UTC)
Where you live? The whole earthly human population is acquiring the isotope signature of C4 plants due to the pervasive use of maize (corn in the USA language), started, presumably by the world invasion of soft-drinks which contain corn syrup. (talk) 19:18, 12 September 2010 (UTC)

Dubious tag[edit]

I've tagged the sentence "Along with CAM photosynthesis, C4 fixation is considered an advancement over the simpler and more ancient C3 carbon fixation mechanism operating in most plants" as dubious. This is because they aren't so much advancements as adaptations. If C4 was an advancement then all plants would use it - the reason they don't is that moving the malate around between cells uses up ATP and therefore C4 plants are outcompeted in colder climates by C3 plants. I get what this sentence is getting at but I don't think it's very accurate. Any suggestions as to how it could be reworded? Smartse (talk) 17:16, 3 May 2009 (UTC)

I think the way you've phrased it will work just fine in the article: C4 fixation is an adaptation made by plants in warmer climates which, in those climates, gives better results for the photosynthetic process. (talk) 13:17, 23 July 2009 (UTC)

Fix the scheme please[edit]

Can someone please draw the scheme of C4 cycle in chemdraw and fix the errors plz? For starters, the pyrophosphate is has P-O-P linkage, not peroxide P-O-O-P link. Next, diagram is hard to read. Thanks. (talk) 01:02, 28 January 2010 (UTC)Ijin


There is a typo in one of the references. The reference is: (#12) Zhu, Xin-Guang,Long, Stephen P;Ort, R Donald (2008). "What is the maximum efficiency with which photoysynthesis can convert solar energy into biomass?". (emphasis added)
Obviously, "Photoysynthesis" is a typo of "Photosynthesis". However, as I am fairly new to wikipedia editing, I do not know how to correct a typo in a reference, so I cannot fix this myself. Pinochet (3) (talk) 20:44, 5 July 2010 (UTC)

Yes check.svg Done Thanks Smartse (talk) 21:05, 5 July 2010 (UTC)

Isotope signature[edit]

C3 plants have a particular carbon isotope signature as stated in the Wikipedia. Then, for consistency it should mentioned in this article whether C4 plants also have such thing. (talk) 19:24, 12 September 2010 (UTC)

C4 photosynthesis NADP-ME type.svg[edit]

In the figure "C4 photosynthesis NADP-ME type.svg" shouldn't the Ala-AT be the MDH (malate dehydrogenase) to go from OA to M? Rej5y7 (talk) 01:50, 12 October 2011 (UTC)

I guess u are right, maybe a c&p-error. --Yikrazuul (talk) 16:01, 13 October 2011 (UTC)

There's another mistake in this diagram - the malic enzyme step that converts malate to pyruvate uses NADP and produces NADPH instead of the other way around as displayed. G22 (talk) 17:42, 22 January 2012 (UTC)

Thx again, fixed it. --Yikrazuul (talk) 19:53, 22 January 2012 (UTC)

Inconsistent percentage of species?[edit]

"Today, C4 plants represent about 5% of Earth's plant biomass and 1% of its known plant species."

"About 7600 species of plants use C4 carbon fixation, which represents about 3% of all terrestrial species of plants." Ted (talk) 17:33, 17 February 2012 (UTC)

Thanks for pointing taht out. I've changed the 1% to 3%, since the source for 3% is comprehensive, listing all the C4 species. From the title, I doubt that the 1% source does so. SmartSE (talk) 13:39, 18 February 2012 (UTC)

Strange text rendering[edit]

I may be going crazy, but at various points in this article where it should read "CO2" or "carbon dioxide", I see the text "plopy plop". I assumed it was vandalism and attempted to change it back, but in editing mode, it appears correct (as "carbon dioxide"). When I went back to reading mode, it was again "plopy plop". I went to a few other sites, and they all render CO2 fine; is this a bug of some kind? — Preceding unsigned comment added by (talk) 23:52, 2 May 2012 (UTC)

Weird! When I search for "plop" I can't find anything. Maybe your computer has some really weird virus. Perhaps try running Spybot – Search & Destroy and malwarebytes (both freeware) and see if it persists. It's much more likely to be at your end than WP's. SmartSE (talk) 23:59, 2 May 2012 (UTC)


it would be nice to have a simplified reaction equation at the beginning of the article like the C3 carbon fixation article does. FoCuSandLeArN (talk) 20:48, 13 September 2012 (UTC)

Dispute of Neutrality or Impartiality[edit]

I dispute the neutrality or impartiality of this sentence in the first paragraph under the subheading "C4 Pathway": The C4 pathway was finally discovered by Marshall Davidson Hatch and C. R. Slack, in Australia, in 1966, so it is sometimes called the Hatch-Slack pathway.[3]

In fact, Hugo Kortschak (and two colleagues with whom he worked) discovered the C4 pathway years before Hatch and Slack performed their work. Kortschak published his results earlier than Hatch and Slack (Kortschak, Hartt, and Burr, 1965). This is attested to by Nickell, 1993. Nickell was the director of the Hawaiian sugar cane research station in which Kortschak conducted his studies in the 1950s and 1960s and was very familiar with Kortschak's research. Nickell goes into great detail about how Kortschak is frequently denied priority and insufficient credit given to him due to the ignorance and neglect of scientists who should know better. In particular, two histories written by Hatch (1992, 2001) both failed to unambiguously give credit to Kortschak for the C4 pathway discovery. As Nickell writes, Hatch and Slack confirmed and greatly extended knowledge about the C4 pathway, but they did not discover it. I have learned that Kortschak presented his research that explicitly documented the C4 pathway in detail possibly as early as 1962 at a scientific conference (see, at which he was publicly criticized by Melvin Calvin himself for claiming that a C4 pathway existed when Calvin had just been awarded the Nobel Prize for discovering the C3 pathway (and much else in the dark reactions). Calvin did not think the C4 pathway could be correct.

The term "Hatch-Slack pathway" is inaccurate and should frankly be abandoned. It should not be repeated in WP. I am going to change the sentence I dispute soon after I receive one more item of historical evidence from a colleague who is a plant physiologist. Steven (talk) 07:17, 29 January 2013 (UTC)

Little mistake light reaction / Calvin cycle?[edit]

I was always learned that the Calvincycle always fixed the CO2, and not the light reactions, which is stated in the article. Is this just a little mistake or am I wrong? — Preceding unsigned comment added by P.zwietering (talkcontribs) 09:27, 28 February 2013 (UTC)

You are correct about the Calvin Cycle (a.k.a. "dark reactions", "light INdependent reactions", "C3 cycle", "reductive pentose phosphate pathway"). The article currently reads, correctly, "In C3 plants, the first step in the light-independent reactions of photosynthesis involves the fixation of CO2 by the enzyme RuBisCO into 3-phosphoglycerate." DB — Preceding unsigned comment added by Devb23 (talkcontribs) 02:27, 23 January 2017 (UTC)

This article needs to talk about stomata[edit]

C4 and CAM photosynthesis make no sense unless stomata are discussed. — Preceding unsigned comment added by Devb23 (talkcontribs) 02:33, 23 January 2017 (UTC)