Photosynthesis Question 62
62. In leaves of $C_4$ plants malic acid synthesis during $CO_2$ fixation occurs in
[2008]
(a) epidermal cells
(b) mesophyll cells
(c) bundle sheath
(d) guard cells
Show Answer
Answer : b
Hints & Solution
(b) In leaves of $C_4$ plants, malic acid synthesis during $CO_2$ fixation occurs in mesophyll cells. The mesophyll cells perform $C_4$ cycle and the cells of bundle sheath perform $C_3$ cycle. $CO_2$ taken from the atmosphere is accepted by phosphoenol pyruvic acid (PEP) present in the chloroplasts of mesophyll cells of these leaves, leading to the formation of a 4-C compound, oxaloacetic acid (OAA). This acid is converted to another 4-C acid, the malic acid which enters into the chloroplast of bundle sheath cells and undergoes oxidative decarboxylation yielding pyruvic acid (3C - compound) and $CO_2$.
