Question

what is the main difference between c3 and c4 carbon fixation?
a in c3 carbon fixation, plant stomata are open during the day, while they are open at night for c4 carbon fixation.
b c3 processes take place throughout the leaf, while c4 processes take place in the inner cells.
c c3 carbon fixation is more common in areas with high light intensity than c4 carbon fixation.
d c3 processes are more efficient than c4 processes in high temperatures.
please select the best answer from the choices provided
a
b
c
d

Explanation:

• Option a: In \(C4\) plants, stomata are open during the day (similar to \(C3\) plants). \(CAM\) plants (not \(C4\)) have stomata open at night. So this option is incorrect.
• Option b: In \(C3\) plants, the Calvin - cycle (carbon fixation) occurs in mesophyll cells throughout the leaf. In \(C4\) plants, the initial carbon fixation (by PEP carboxylase) occurs in mesophyll cells, and the Calvin - cycle occurs in bundle - sheath cells (inner cells). This is a key structural and functional difference.
• Option c: \(C4\) carbon fixation is more common in areas with high light intensity (and high temperatures) compared to \(C3\) fixation. So this option is incorrect.
• Option d: \(C4\) processes are more efficient than \(C3\) processes in high temperatures because \(C4\) plants can reduce photorespiration (a wasteful process in \(C3\) plants under high - temperature and high - light conditions). So this option is incorrect.

Answer:

B. C3 processes take place throughout the leaf, while C4 processes take place in the inner cells.