Talk:Crassulacean acid metabolism

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What does this meen?[edit]

What dose this meen? Maybe put it up in simpler tearms please? 01:21, 1 October 2006 (UTC)

I don't think an article on CAM is going to be the kind of simple I believe you are referring to. 06:25, November 7, 2006

separating carbon fixation from the calvin cycle?[edit]

Thus, C4 metabolism physically separates CO2 fixation from the Calvin cycle, while CAM metabolism temporally separates CO2 fixation from the Calvin cycle.

I thought that CO2 fixation was synonymous with the Calvin cycle? Also, why do we refer to it as the 'Calvin-Benson cycle' here. I've only heard 'calvin cycle.' Is the other name more common somewhere else in the world other than the US? Otherwise, it easily spreads confusion.--Ryan Wise 07:59, 6 May 2007 (UTC)

For Calvin-Benson see [1] and [2] Jclerman 09:19, 6 May 2007 (UTC)
For "c4 carbon fixation" see [3] and other references.

Jclerman 09:26, 6 May 2007 (UTC)

I can't provide sources, but I'm sure with some brief research you can confirm what I'm telling you right now. First of all, CO2 fixation isn't exactly synonymous with the Calvin-Benson cycle; it's more like the Calvin-Benson cycle is a form of carbon fixation. What the quote you gave was discussing the process of carbon fixation in C4 and CAM plants and how it differs from the typical C3 plants. To understand why plants sometimes go through C4 or CAM carbon fixation, you need to know that RuBisCO, the main enzyme that catalyzes carbon fixation, is also capable of accepting an oxygen molecule (O2) instead of a carbon dioxide, and when this occurs, no carbon fixation occurs, thus wasting the plant's resources (photorespiration). This means that if the carbon dioxide concentration isn't high enough, then photorespiration is much more likely to occur than carbon fixation so some plants have evolved to fix this problem by increasing the concentration of carbon dioxide within the plant. For C4 and CAM plants, they will initially fix carbon into a 4-carbon compound (thus C4) that can later be broken up to release carbon dioxide. For C4 plants, their RuBisCO is separated from atmospheric oxygen while the carbon dioxide concentration is increased around the enzyme by breaking up the 4-carbon compound which is why C4 photosynthesis physically separates CO2 fixation. In CAM plants, instead of isolating RuBisCo, they simply fix as much CO2 as they can during the night and close off their stomata during the day to prevent water loss and oxygen intake, and the 4-carbon compound is broken up to release carbon for photosynthesis during the day. This is why you often see CAM photosynthesis in plants that live in dry climates, and it's also how CAM separates carbon dioxide fixation temporally (by time).

To answer your second question about why the Calvin cycle is referred to as the Calvin-Benson cycle. I guess Melvin Calvin (the Calvin part of the Calvin-Benson cycle) was the main professor overseeing the research on this cycle, thus when the results first came out, he got most of the credit. However, Andrew Calvin, one of Dr. Calvin's graduate students/research assistant, actually did quite a bit of the research too, so some people have started to credit him in the light independent cycle as a result, although this is not universally adopted. MonkeysOnThePatio (talk) 22:21, 15 February 2012 (UTC)

Daytime/Nighttime Difference in Taste[edit]

Is there also suppose to be a difference in taste (like in pineapples) depending on the level of malic acid present in day vs night? (talk) 11:28, 6 February 2008 (UTC)

Yes. Late afternoon vs early morning tissues taste different, due to the malic acid depletion in the first group. Jclerman (talk) 20:30, 6 February 2008 (UTC)


Hi, I've re-written this article, as I found it rather difficult to follow. I've tried to combine the information that was there with my own knowledge so hopefully haven't strayed too wide of the mark; however I would be grateful if someone with a level of expertise were to take a look through the article, particularly at the statements marked [verification needed]! I've also removed the "Expand" notice, as I think the article is reasonably comprehensive (while being very concise). More helpful than a boilerplate notice would be specific {{expand section}} notes, or better still a mention of weak areas on this talk page. Thanks! Verisimilus T 19:35, 11 February 2008 (UTC)

CAM must have evolved more than twice - it appears to have evolved 3 or 4 times in Bromeliaceae alone. One source says it is found in 33 families and 328 genera, and the count has probably increased since. The only immediately obvious candidate for a multi-familial group with a shared origin of CAM is (suborder) Portulacineae, i.e. Portulacaceae, Cactaceae, Didieraceae, Basellaceae, etc. I guess that it has evolved 40 or 50 times, but since all the lists seem to either been behind paywalls or not online, it's not easy to match the taxonomic distribution to the APG cladogram.
When I was skimming papers last night one paper listed about half-a-dozen different modes of CAM (not including the terrestrial/aquatic dichotomy), so the full or partial column in the table may need modifying. Also what it meant by evolving CAM may not be clear cut. (I'll have a closer look at some of those papers when I have time.)
I get the impression that the orchidaceous clade that displays CAM excludes Orchis - the Angiosperm Phylogeny Website suggests that it is Epidendroideae.
Terrestrial CAM plants are commonly plants which are under water stress, whether plants of arid environments (xerophytes), plants that grow on other plants and are dependent on rain rather than soil moisture (epiphytes), and plants that grow in salty habitats (halophytes). I saw a suggestion that succulence - also an adaptation to water stress - is prerequisite for the evolution of CAM.
It would be handy to know what the metabolic differences between CAM and C3 plants are - I assume that most of the cycle takes advantage of preexisting metabolic processes. Lavateraguy (talk) 20:43, 12 February 2008 (UTC)
I can access most articles behind "paywalls", so let me know if there are any PDFs you would like me to send you. As I understand it, it's the PEP -> oxaloacetate -> malate -> pyruvate cycle that allows plants to "do" CAM - but I thought this was present in C3 plants too? (I'm very rusty on my metabolisms!) It's true that most CAM plants are succulents, but it's interesting that isoetes - a lycopsid, about as far removed from the "traditional" CAM plants as you can get! - do it too. I guess succulence isn't monophyletic either, and Isoetes is quite "juicy"... I'm not sure how much is known about the evolution of CAM, though, and would be very interested if you come across more details! Thanks again for your help with this article. Verisimilus T 21:55, 12 February 2008 (UTC)
I've started putting together an alternative table of CAM plants at my talk page Lavateraguy (talk) 21:42, 14 February 2008 (UTC)
You could have a look at Jon E. Keeley, Distribution of Diurnal Acid Metabolism in the Genus Isoetes, American Journal of Botany 69(2): 254-257 (1982) to see what it says explicitly or implcitly about the phylogenetic distribution of CAM is Isoetes. Lavateraguy (talk) 02:09, 15 February 2008 (UTC)
A promising looking reference is Smith, J. A. C. & K. Winter. 1996. Taxonomic distribution of crassulacean acid metabolism. Pp. 427-436. In K. Winter & J. A. C. Smith (Eds.). Ecological studies, analysis and synthesis, Vol 114. Crassulacean acid metabolism: biochemistry, ecophysiology and evolution (449 pp.). Springer-Verlag , New York Lavateraguy (talk) 21:35, 21 February 2008 (UTC)
If someone could take a look at - it looks from Google as if it has a table of CAM plants, but it's behind a paywall so I can't check it out myself. (BTW, I've now built a list of 40 families containing CAM plants, though I haven't been able to find adequately specific references for all of them.) Lavateraguy (talk) 21:42, 21 February 2008 (UTC)


The image of the cycle seems to keep being incorporated as a thumbnail. It is completely illegible at under 500px width, so I don't see any point in putting in a small image - better, I think, to have it as a "see also". Please feel free to convince me otherwise! Thanks. Verisimilus T 12:23, 12 February 2008 (UTC)

The function of a thumbnail is giving the user an idea of what the picture is about and not showing its actual resolution. Sure, if the picture is a little bit larger, the thumbnail picture cannot show it in detail. Moreover, in my opinion, the article is a little bit too cursorily, but the pathway overview might be too detailed for the text above. Either an extra article about the CAM biochemistry or an extra chapter in this article is necessary for users who search more than some general information. That's why, I create a new chapter called "Biochemistry of Crassulacean acid metabolism" and hope that I can contribute a text to it as soon as possible. --Crenim (talk) 19:05, 13 February 2008 (UTC)

Biochemistry of CAM[edit]

So, I've written a short introduction for users who want to know more about the biochemical details of CAM. Since, a detailed description would filled a couple of pages, I adapt the passage on the figure. It would be very nice, if somebody would proofread this text and maybe correct wrong parts.--Crenim (talk) 11:53, 14 February 2008 (UTC)

Great stuff, thanks for your contribution. Afraid I don't know enough to comment on its accuracy though! Verisimilus T 12:46, 14 February 2008 (UTC)
Photosynthesis: A Comprehensive Treatise at Google Books might be of some use Lavateraguy (talk) 22:22, 14 February 2008 (UTC)

aquatic CAM plants[edit]

CAM occurs not only in terrestrial plants, typically those which encounter seasonal, intermittent or permanent water stress (xerophytes, epiphytes, lithophytes), but in aquatic plants, where its advantage lies in increased fixation of scarce CO2, rather than conservation of water. This should be reflected in the article. Lavateraguy (talk) 20:49, 15 February 2008 (UTC)

Reference(s)? Jclerman (talk) 09:28, 17 February 2008 (UTC)
See User_talk:Lavateraguy#CAM_plants; there's about five (small) groups of hydrophytes listed there, though in some cases there is disagreement in the literature as to whether they are CAM plants or C4 plants. There's also Crassula aquatica. Lavateraguy (talk) 19:05, 17 February 2008 (UTC)

strong and weak CAM?[edit]

Or variability of the degree of CAM? (See User_talk:Lavateraguy#CAM_plants). In the online abstract of one of the cited references: "Degrees of crassulacean acid metabolism in tropical epiphytic and lithophytic ferns", Holtum and Winter state that several species

  • "....exhibited carbon isotope ratios of between -25.9 and -11;22.6 per mil ; indicating that carbon isotope ratios may not, by themselves, be sufficient for the identification of weak CAM...."

Could you please post or email me the full article? I can only access the abstract and would like to understand how they arrive to such conclusion since the isotope compositions are not a direct measurement of the strength or weakness of CAM. Funct Plant Biol, Austr J Plant Phys, 26(8), 749-757 (1999). Jclerman (talk) 20:43, 17 February 2008 (UTC)

On it's way via e-mail. Interesting find! Verisimilus T 08:55, 18 February 2008 (UTC)
Thanks a lot. A fast reading shows that the measurements of isotope compositions can't be used for the intended discussion. The relevant variable is the isotope discrimination rather than the isotope composition. Jclerman (talk) 17:30, 19 February 2008 (UTC)

List of CAM plants[edit]

I've produced a completish list of plants displaying Crassulacean Acid Mechanism, but it needs reworking by someone who can get behind paywalls to read the literature. (The confusion as to which Hydrocharitaceae are CAM plants, and which are C4 plants, also needs looking into.) Lavateraguy (talk) 13:54, 24 February 2008 (UTC)

Stomata do open in the day[edit]

Many CAM plants do in fact open their stomata during the day once the accumulated malic acids have been used up. The article needs changing accordingly. Smartse (talk) 13:41, 15 April 2009 (UTC)

Assuming this is true (I suspect it is but am not familiar with the relevant literature) then a lot of the article is quite misleading. Nobody has posted to disagree with you in over two years so I think it's worth adding an "expert attention" tag to the article to settle the matter. Does the "night" portion of the cycle even have anything to do with a response to darkness or is it entirely a function of temperature and humidity? Will some CAM-only plants die under 24 hour light even if the temp and humidity are what they would be at night in their native habitat?--Eloil (talk) 02:31, 8 October 2011 (UTC)

What temperature?[edit]

"CAM plants open their stomata during the cooler and more humid night-time hours, permitting the uptake of carbon dioxide with minimal water loss." and what temperature might that be? How much different from daytime? Is it the different temperature between night and day, or a specific temperature? (talk) 05:33, 27 April 2009 (UTC)

Error in the metabolism chart[edit]

The metabolism chart shows malate entering the vacuole and becoming maleic acid. Since the process shows addition of two protons rather than removal of H2O, it should say malic acid. (talk) 21:31, 16 March 2010 (UTC)

Incorrect citation removed[edit]

Re the dubious Peperomia citation, I forwarded the following email to the Michigan Dental Hygenists Association.

 Dear Sir/Madam,
 I wonder if you could help solve a mystery? An article in your journal dating back to 1975,
 "Bull Mich Dent Hyg Assoc. 1975 Sep;5(3):4. Editorial: Who am I if I am not a tooth scraper? Catallo SL. PMID: 1064456",
 appears to be being used on Wikipedia as a reference as to the correct photosynthetic pathways used by a certain small epiphytic plant growing on rotting wood (Peperomia spp).
 It seems highly unlikely to me that a journal of dental hygenists based in Michigan would contain an article on adaptations to carbon fixation in plants in arid climates, however I am unable to secure a copy of your journal, despite having access to a large copyright library.
 I wonder if you could help shed light this mystery, by whatever mecahnism is the most convenient for you? I could then correct the mistake, if mistake it is.
 All the best,

They graciously replied with a back issue which confirms that this citation has nothing at all to do with the subject in question, so I will remove it and look to see if I can shed any light on why it might have been added in the first place, in case the error is more pervasive. (talk) 09:38, 27 May 2010 (UTC)

Ok, tracked down the issue. Seems to be to do with IDs. Have mailed bioinformatician who knows about such things, but it seems that the correct ids are known as PMC ids, and these have been substituted with the PMID at some point in the past, which points to a different article. (Either that, or the two sites I find disagree on the paper at each ID point). Found one more obvious mistake (another 1970s dentistry reference), and fixed it, but don't have time to be systematic at the moment, as that will need some kind of automation.

Thanks again to the Michigan Dental Hygenist's Association for their co-operation with someone half way around the world from them with an interest in pineapples. (talk) 09:56, 27 May 2010 (UTC)

Thanks for noticing this and tracking it down. I slightly revised your fix, by bringing back {{cite journal}}, changing pmid to pmc, adding the correct pmid (which is on the pubmed central page), deleting the rest of the incorrect citation, and running citation bot. The offending edit in this case was only a week or so ago; see [4]. I glanced through that edit, and found one more. I also left a (friendly) message on the talk page of the user who made it. See Help:Page history for more detail on article history if you're not familiar with it. Kingdon (talk) 11:27, 2 June 2010 (UTC)

strange isotope composition[edit]

is mentioned for other plants and in other articles, missing in this one... (talk) 01:22, 13 September 2010 (UTC)

It would appear to warrant a brief mention with a link to δ13C and/or Isotopic signature#Carbon isotopes. I don't see Crassulacean acid metabolism as a place to go into much detail, however. Kingdon (talk) 13:28, 27 September 2010 (UTC)


There's a less efficient use of CAM, called CAM-cycling, in which CO2 from respiration is stored for later use, either at night or when water stress causes stomata to close during daylight. This isn't discussed at all in the article. It's briefly described in this paper, which I've used at Cactus#Metabolism, and in more detail in this paper. It should be added here if someone can do so. Peter coxhead (talk) 22:07, 27 February 2012 (UTC)

I've now reworked the article with two main purposes:
  1. I've reorganized it so that CAM itself is discussed first, then its use by plants.
  2. I've clarified that there are a range of different uses of CAM by plants, from full obligate CAM through to CAM-cycling. (These uses could all do with expanding, particularly the difference between "strong CAM" and "weak CAM".)
  3. For this reason I've changed occurrences of the phrase "CAM plant" in the running text: it's not clear whether this phrase means "a plant which can use CAM to some degree" or "an obligate CAM using plant".
I don't claim to be an expert, but I think I have at least begun to resolve a number of issues raised above, so I've removed the "attention required" tag. Peter coxhead (talk) 12:49, 29 February 2012 (UTC)