Question

Refer to the given cross section of a $C_4$ leaf and select the incorrect option.

• A. P are the chloroplasts in which thylakoids are stacked together to form grana
• B. P are the chloroplasts which can perform light reaction, evolve molecular $O_2$ and produce assimilatory power
• C. Q are the chloroplasts in which thylakoids occur as stroma lamellae.
• D. Q are the chloroplasts in which $C{O}_2$ is fixed by phosphoenol pyruvic acid to form oxaloacetic acid

Answer 1

Answer: (D)

The given cross section of the leaf represents Kranz anatomy in a $C_4$ plant. $P$ are the chloroplasts of mesophyll cells, which are granal (/.a, thylakoids are stacked to form grana) j and are specialised to perform light reaction of photosynthesis, evolve $O_2$ and produce assimilatory power $(ATP+NADP{H}_2)$. $Q$ are the chloroplasts of bundle sheath cells which are agranal, i.e., grana are absent and the thylakoids occur as stroma lamellae. In these chloroplasts, final fixation of $C{O}_2$ takes Ptace through Calvin cycle where $C{O}_2$ is fixed by $RuBP$ in the presence of enzyme $RuBisCO$.