How do C3, C4, and CAM plants differ in their photosynthetic processes?

C3, C4, and CAM plants differ in their photosynthetic processes based on their carbon fixation methods and adaptation to environmental conditions.

C3 plants, named for the three-carbon compound produced during photosynthesis, follow the traditional photosynthetic pathway. They use the enzyme Rubisco to fix carbon dioxide directly from the air, converting it into a three-carbon compound, 3-phosphoglycerate. This process occurs in the mesophyll cells of the leaf. However, C3 plants are less efficient in hot and dry conditions as Rubisco can bind with oxygen instead of carbon dioxide, leading to photorespiration which wastes energy and carbon.

C4 plants, on the other hand, have evolved a different mechanism to overcome the inefficiency of Rubisco. They initially fix carbon dioxide into a four-carbon compound, oxaloacetate, in the mesophyll cells. This compound is then transported to the bundle-sheath cells where it releases carbon dioxide, which is then fixed by Rubisco into a three-carbon compound. This spatial separation of carbon fixation and the Calvin cycle reduces photorespiration, making C4 plants more efficient in hot and dry conditions.

CAM (Crassulacean Acid Metabolism) plants have evolved a unique adaptation to survive in extremely arid conditions. They fix carbon dioxide at night when the temperature is cooler and store it as a four-carbon compound, malate. During the day, when the stomata are closed to prevent water loss, the stored malate is decarboxylated to release carbon dioxide, which is then used in the Calvin cycle. This temporal separation of carbon fixation and the Calvin cycle allows CAM plants to minimise water loss, making them highly efficient in desert conditions.

In summary, while all three types of plants perform photosynthesis to produce energy, they differ in their carbon fixation methods and their adaptations to environmental conditions. C3 plants follow the traditional photosynthetic pathway, C4 plants have a spatial separation of carbon fixation and the Calvin cycle, and CAM plants have a temporal separation of these processes. These adaptations allow each type of plant to thrive in different environmental conditions.