In C₄ plants, Calvin cycle

Question

Question

This question was previously asked in

HPSC Assistant Professor 2018 Botany (Official Paper)

Answer 1

The correct answer is occurs in stroma of bundle sheath chloroplasts.

Concept:

C4 plants have a unique mechanism to efficiently fix carbon dioxide (CO₂) and minimize photorespiration.
The Calvin cycle is a set of biochemical redox reactions that occur in the stroma of chloroplasts in photosynthetic organisms.
In C4 plants, the Calvin cycle is spatially separated from the initial CO₂ fixation.

Explanation:

Option 1: occurs in stroma of bundle sheath chloroplasts: This is the correct answer. In C4 plants, the Calvin cycle takes place in the stroma of bundle sheath chloroplasts. This spatial separation allows C4 plants to efficiently fix CO₂ and minimize photorespiration.
Option 2: occurs in grana of bundle sheath chloroplasts: This is incorrect. The Calvin cycle does not occur in the grana; it takes place in the stroma. The grana are involved in the light-dependent reactions of photosynthesis.
Option 3: occurs in mesophyll of chloroplasts: This is incorrect. In C4 plants, the initial CO₂ fixation occurs in the mesophyll cells, but the Calvin cycle takes place in the bundle sheath cells.
Option 4: does not occur as CO₂ is fixed mainly by PEP and no CO₂ is left for Calvin cycle: This is incorrect. While it is true that CO₂ is initially fixed by phosphoenolpyruvate (PEP) in the mesophyll cells, the CO₂ is then transported to the bundle sheath cells where it enters the Calvin cycle.