The CAM plants represent a metabolic strategy adapted to extremely hot and dry environments. They represent about 10% of the plant species and include cacti, orchids, maternity plant, wax plant, pineapple, Spanish moss, and some ferns. The only agriculturally significant CAM plants are the pineapple and an Agave species used to make tequila and as a source of fiber.
The sketch below of the day-night cycle of the CAM plants is patterned after Moore, et al. The name Crassulacean Acid Metabolism came from the fact that this strategy was discovered in a member of the Crassulaceae which was observed to become very acidic at night and progressively more basic during the day.
How CAM plants handle the O2 evolved in photosynthesis during daytime
The acidity was found to arise from the opening of their stomata at night to take in CO2 and fix it into malic acid for storage in the large vacuoles of their photosynthetic cells. It could drop the pH to 4 with a malic acid concentration up to 0.3M . Then in the heat of the day, the stomata close tightly to conserve water and the malic acid is decarboxylated to release the CO2 for fixing by the Calvin cycle. PEP is used for the initial short-term carbon fixation as in the , but the entire chain of reactions occurs in the same cell rather than handing off to a separate cell as with the C4 plants. In the CAM strategy, the processes are separated temporally, the initial CO2 fixation at night, and the malic acid to Calvin cycle part taking place during the day.
Types of Photosynthesis: C3, C4 and CAM
The fundamental principle of photosynthesis is that plants open and close the stomata (pores) on the leaves, and thus control the amount of carbon dioxide and oxygen that passes through them.
C3 C4 CAM Plants & Photorespiration - YouTube
C3 plants have the disadvantage that in hot dry conditions their photosynthetic efficiency suffers because of a process called . When the CO2 concentration in the drops below about 50 ppm, the catalyst that helps to fix carbon begins to fix oxygen instead. This is highly wasteful of the energy that has been collected from the light, and causes the rubisco to operate at perhaps a quarter of its maximal rate.
Crassulacean Acid Metabolism | ASU - Ask A Biologist
The exact nature of photosynthesis is determined by the temperature, the sunlight, the carbon dioxide, the water and the general weather conditions that a plant is exposed to.
C3 Photosynthesis - Georgia State University
fluence for tobacco and maize in ambient oxygen (21%); (b) light saturation point - point at which increasing fluence yields a constant amount of photosynthesis; (c) light compensation point - fluence at which the amount of photosynthesis just equals the amount of respiration; and (d) note that plants that photorespire (like tobacco) have a higher light compensation point and light saturate.