Question

Distinguish between C3, C4, and CAM plants in terms of their basic physiology, anatomy (Hint: do they have specialized structures?), and the type of environment they are typically found.

Answer 1

The key difference between the C3, C4 and CAM plants is the assimilation of carbondioxide and converting them to glucose to synthesize different products. In C3 plants, the cells involved are mesophyll cells,

C3 plants:

These plants are cold season or temperate plants whuch grow at an optimum temperature of 65 to 75°F with soil temperature of 40 to 45°F having less efficiency at high temperatures. The cells involved in this photosynthesis are mesophyll cells. They produce carbondioxide directly in chloroplast. These plants are either perennial or annual which is highly proteinaceous than C4 plants. Majority of plants use C3 photosynthetic pathway. It is the oldest photosynthetic pathway among higher plants. During geological time, plants evolved that can perform better in unfavourable conditions than C3 plants which used two alternatives for C3 photosynthesis namely C4 plants and CAM plants. Eg: wheat, oats, rye, etc.

C4 plants:

Also called as Hatch and Slack pathway. It occurs in mesophyll and bundle sheath cells present in chloroplats. They are warm season or tropical plants and can be perennial or annual growing at temperature of 90to 95°F. They are more efficient in utilizing nitrogen and carbondioxide from soil and atmosphere respectively with less protein content. Eg: Indian grass, corn, etc. C4 and CAM plants are separated in time allowing the plant to reduce day time water loss by evaporation. The leaf tissue is separated into 2 specialized compartments namely photosynthetic assimilation and photosynthetic reduction tissue(PCR) alligned in symmetrical patterns with only single mesophyll tissue between intracellular air space and PCR tissue for optimal transport. This is called as Kranz anatomy.

CAM plants: (Crassulacean Acid Metabolism)

Its a adaptation of periodic drought. It is oldest alternative to C3 plants. Found in modern day dessert plants thai is hot and dry environments. These plants have special morphological features like large vacuoles for carbon and water storage giving succulent appearance to tissues. They have thick cuticles with stomata which acts as a barrier for water loss by evaporation. Eg. Opuntia, aloe, etc. Aquatic CAM plants do not suffer from water loss. Most of them are angiosperms.