Question

Assertion (A): Manganese deficiency in plants primarily affects the photosynthetic process.
Reason (R): Manganese is a cofactor for several enzymes involved in the photosynthetic electron transport chain, facilitating electron transfer reactions within chloroplasts.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
• C. (A) is correct but (R) is not correct.
• D. (A) is not correct but (R) is correct.

Hint:

Manganese's key role in photosynthesis makes its deficiency particularly harmful to plant growth.

Answer 1

The Correct Option is A

Manganese plays a critical role in photosynthesis, particularly in the oxygen-evolving complex of photosystem II. Deficiency directly impacts this process.

Answer 2

Mechanistic link: Photosystem II houses the oxygen-evolving complex, a manganese cluster (\( \text{Mn}_4\text{CaO}_5 \)) that stores oxidising equivalents and splits water into oxygen, protons, and electrons.
When manganese is deficient, this cluster cannot assemble properly, so water-splitting and the resulting electron flow into the photosynthetic electron transport chain slow down, directly impairing photosynthesis, which is exactly the causal chain the assertion describes.
Because the reason identifies the precise biochemical site where manganese acts, it fully explains why its deficiency affects photosynthesis, so both statements are true and R explains A.