Talk:Crassulacean acid metabolism

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What dose this meen? Maybe put it up in simpler tearms please? 218.214.20.214 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 202.172.125.45


Contents

[edit] separating carbon fixation from the calvin cycle?

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)

[edit] Daytime/Nighttime Difference in Taste

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? 71.114.181.145 (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)

[edit] Rewrite

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 http://www.amjbot.org/cgi/content/abstract/94/10/1670 - 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)

[edit] Image

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)

[edit] Biochemistry of CAM

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)

[edit] aquatic CAM plants

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)

[edit] strong and weak CAM?

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)

[edit] List of CAM plants

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)