Question

Different types of photosynthesis occur depending on the environmental conditions and the type of plant. Which type of photosynthesis occurs in plants in hot dry conditions?
I. $C_3$ photosynthesis
II. $C_4$ photosynthesis
III. $CAM$ photosynthesis

• A. I only
• B. II only
• C. III only
• D. I and II only
• E. II and III only

Answer 1

Answer: (E)

II and III only

I. C3 pathway, also known as Calvin cycle, is the major pathway for the fixation of carbon dioxide in green plants. The reactions are enzyme controlled and temperature dependent.

II. C4 plants have C4 pathway for carbon fixation which is also called Hatch and Slack pathway. Efficiency of C4 pathway increases up to 50% on increasing temperature to about 35°C.

III. CAM (Crassulacean Acid Metabolism) plants are mostly succulent xerophytes such as plants of family Crassulaceae, Cactaceae etc. Stomata in these plants remain closed during the day to check transpiration and open at night during the cool night for gaseous exchange.

Hence the type of photosynthesis that occurs in plants in hot dry conditions is C4 photosynthesis and CAM photosynthesis.

So, the correct answer is 'II and III only'.