CAM Plants with Bonnie, Colt, and Henry

There are many different types of Crassulacean acid metabolism (CAM) plants. CAM plants are plants that open their stomata at night. This allows carbon to be temporarily stored at night (Keeley, 1998). The CO₂ fixation is stored in the form of malic or isocitric acid during the night (photosynthesis-cam). During the light hours the acid is broken down releasing CO₂ that is used in the Calvin Cycle. Historically CAM plants have been thought of as being desert or dry climate plants. In fact, most CAM plants are desert plants, but some species of aquatic plants have been found to be CAM plants. It is difficult to generalize about all CAM plants. There are some plants that perform both C3 and CAM photosynthesis. There are also some plants that perform C4 and CAM photosynthesis (Guralnick, 2008). CAM plants consist of many different kinds of plants. This paper will look at the different kinds of CAM plants and the different aspects of CAM photosynthesis.

The largest proportion of CAM plants can be found in desert with dry climates. These plants date back to the Pleistocene era, but many researchers believe they may date back to the Mesozoic era (Wit, 2006). It is believed that these plants evolved CAM photosynthesis in an effort to reduce water loss. Transpiration through stomata is the main way in which plants lose water. In dry conditions, plants can lose large amounts of water to the atmosphere if their stomata are open during the day. CAM plants have adapted the ability to open their stomata during the night when there is less transpiration. They have the ability to take in CO₂, store it, and use it during the day time. This results in less transpiration because their stomata do not have to open during the day. This is an important adaptation in climates where water is scarce.

It was once accepted that CAM plants were all desert plants, but recent research shows that many CAM plants live in aquatic condition. There have been many different documented aquatic CAM plants, such as Isoëtes and some monocots and dicots (Keeley, 1998). Keeley (1998) states, "Aquatic CAM plants inhabit sites where photosynthesis is potentially limited by carbon" (p. 121). Aquatic CAM plants are not concerned with water loss, but rather are concerned with a limited amount of CO₂. There is an elevated amount of CO₂ at night and aquatic CAM plants are able to take advantage of the elevated amount and store it for photosynthesis (Keeley, 1998). This is an evolutionary advantage for plants without the ability to take in CO₂ at night. Aquatic CAM plants do not posses stomata that regulate gas exchange; rather they have tissue that restricts the diffusion of gasses into the water (Keeley, 1998).

Not only are CAM plants unique in that they are found in both desert and aquatic environments, but some also have a unique characteristic that they may not always perform CAM photosynthesis. Some plants exhibit both CAM and C3 photosynthesis. These plants can switch from one type of photosynthesis to another dependent upon the environmental conditions. For example, "...the CO₂ exchange pattern in K. pinnata was converted from CAM to C3 mode at the dark temperature of 37°C with loss of nocturnal CO₂ absorption" (Metabolic, 2006, p. 15). It seems that if environmental conditions are not advantageous for a plant to perform CAM photosynthesis, it will revert back to C3 photosynthesis. There have also been reports that some CAM plants also perform C4 photosynthesis. Guralnick (2006) states, "In the Portulaca, CAM succulent tissue is overlaid with the C4 tissue in a unique fashion where both pathways are operating simultaneously."

Another interesting aspect of CAM photosynthesis is that they can CAM idle (TYPES OF PHOTOSYNTHESIS, 2004). This means that when environmental conditions become extremely bad, the plant can completely close their stomata. When the plant does this it uses the oxygen produced from photosynthesis to respire, and uses the CO₂ produced from respiration for photosynthesis (TYPES OF PHOTOSYNTHESIS, 2004). CAM idling allows plants to cope with severe conditions but can only be sustained for a limited about of time.

CAM photosynthesis is a unique type of photosynthesis that allows certain plants to cope with extreme environmental conditions. Whether the conditions are extremely dry or CO₂ deficient, CAM plants have adapted the ability to fix CO₂ at night in an acid and release it during the day to be used in photosynthesis. CAM plants are able to adapt to different environmental conditions using CAM idling or changing to C3 or C4 photosynthesis. They are indeed unique types of plants.

[1]Keeley, J. E. (1998). CAM Photosynthesis in Submerged Aquatic Plants. The Botanical Review 64, 121-175.

Footnote:
1. Keeley, J. E. (1998). CAM Photosynthesis in Submerged Aquatic Plants. The Botanical Review 64, 121-175.

Footnote:
2. photosynthesis-Cam. (n.d.). Retrieved March 30, 2009, from Photosynthesis - History Of Research, Location Of Light Reactions, Cam Photosynthesis, Photorespiration, Cyanobacteria, Anaerobic Photosynthetic Bacteria - Light reactions, Dark reactions, Photosynthesis in lower organisms, Chloroxybacteria : http://science.jrank.org/pages/5191/Photosynthesis-CAM-photosynthesis.html

[3]Guralnick, L. J. (2008, June 28th-29th). Evolutionary physiology: the extent of C4 and CAM photosynthesis in the genera Anacampseros and Grahamia of the Portulacaceae. Retrieved 2009, from Journal of Experimental Botany: http://jxb.oxfordjournals.org/cgi/content/abstract/ern081

Footnote:
3. Guralnick, L. J. (2008, June 28th-29th). Evolutionary physiology: the extent of C4 and CAM photosynthesis in the genera Anacampseros and Grahamia of the Portulacaceae. Retrieved 2009, from Journal of Experimental Botany: http://jxb.oxfordjournals.org/cgi/content/abstract/ern081

[4]Wit, J. E. (2006). Carbon Isotope evidence for CAM photosynthesis in the Mesozoic. AEON, 9-17

Footnote:
4. Wit, J. E. (2006). Carbon Isotope evidence for CAM photosynthesis in the Mesozoic. AEON, 9-17

Footnote:
5. Keeley, J. E. (1998). CAM Photosynthesis in Submerged Aquatic Plants. The Botanical Review 64, 121-175.

Footnote:
6. Keeley, J. E. (1998). CAM Photosynthesis in Submerged Aquatic Plants. The Botanical Review 64, 121-175.

Footnote:
7. Keeley, J. E. (1998). CAM Photosynthesis in Submerged Aquatic Plants. The Botanical Review 64, 121-175.

[8]Metabolic, E. O. (2006). Effects of High Night Temperature on Crassulacean Acid Metabolism (CAM) Photosynthesis of Kalanchoe pinnata and Ananas comosus . Planet Prod. Sci. 9 , 10-19.

Footnote:
8. Metabolic, E. O. (2006). Effects of High Night Temperature on Crassulacean Acid Metabolism (CAM) Photosynthesis of Kalanchoe pinnata and Ananas comosus . Planet Prod. Sci. 9 , 10-19.

Footnote:
9. Guralnick, L. J. (2008, June 28th-29th). Evolutionary physiology: the extent of C4 and CAM photosynthesis in the genera Anacampseros and Grahamia of the Portulacaceae. Retrieved 2009, from Journal of Experimental Botany: http://jxb.oxfordjournals.org/cgi/content/abstract/ern081

[10]TYPES OF PHOTOSYNTHESIS. (2004, May). Retrieved 2009, from Desert Ecology of Tucson, AZ: http://wc.pima.edu/~bfiero/tucsonecology/plants/plants_photosynthesis.htm

Footnote:
10. TYPES OF PHOTOSYNTHESIS. (2004, May). Retrieved 2009, from Desert Ecology of Tucson, AZ: http://wc.pima.edu/~bfiero/tucsonecology/plants/plants_photosynthesis.htm

Footnote:
11. TYPES OF PHOTOSYNTHESIS. (2004, May). Retrieved 2009, from Desert Ecology of Tucson, AZ: http://wc.pima.edu/~bfiero/tucsonecology/plants/plants_photosynthesis.htm