Photosynthesis Question 94
94. In $C_4$ plants, Calvin cycle operates in
[1989]
(a) Stroma of bundle sheath chloroplasts
(b) Grana of bundle sheath chloroplasts
(c) Grana of mesophyll chloroplasts
(d) Stroma of mesophyll chloroplasts
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Answer : a
Hints & Solution
(a) $C_4$ plants are specialised plants for better $CO_2$ assimilation found in hot environment. They have a characteristic leaf anatomy called kranz anatomy showing two distinct choloroplast containing cells mesophyll and bundle sheath cells. Mesophyll cells are located very near to bundle sheath cells and are the site for $C_4$ cycle i.e. $CO_2$ is first fixed as a 4 carbon compound oxaloacetic acid by the action of PEP carboxylase. The second carboxylation event occurs in stroma of chloroplast of bundle sheath cell through $C_3$ cycle.
