Plant Physiology- ICAR JRF/SRF 2024

• Assertion (A) is True: Dry matter partitioning dynamically balances vegetative biomass between the root and shoot systems (functional equilibrium).
• Reason (R) is True & Explains (A): Coordinated partitioning ensures that shoot photosynthetic assimilate production is matched by root absorption of water and mineral nutrients, maintaining balanced whole-plant stoichiometry.
• Conclusion: Both (A) and (R) are true and (R) is the correct explanation of (A).

Correct option: (1) Both (A) and (R) are true and (R) is the correct explanation of (A)

• Statement (I) is True: Reactive oxygen species ($\text{O}_2^{\bullet-}$, $\text{H}_2\text{O}_2$, $^{\bullet}\text{OH}$) initiate self-propagating free-radical chain reactions of lipid peroxidation in polyunsaturated fatty acids, disrupting membrane fluidity and inducing cell death.
• Statement (II) is True: Plants genetically adapted to thrive under high salt concentrations ($\gt 200\text{ mM NaCl}$) are classified as halophytes, whereas non-adapted, salt-sensitive species are classified as glycophytes.
• Conclusion: Both Statement (I) and Statement (II) are true.

Correct option: (1) Both Statement (|) and Statement (II) are true.

• Statement (I) is True: Heat stress directly disrupts weak hydrogen bonds and hydrophobic interactions, leading to membrane hyperfluidity and structural denaturation of protein complexes.
• Statement (II) is False: The primary physical lesion of cold/freezing stress is membrane rigidification and phase transition from a flexible liquid-crystalline to a solid gel phase, inducing electrolyte leakage and dehydration, NOT disturbed cofactor binding.
• Conclusion: Statement (I) is true but Statement (II) is false.

Correct option: (3) Statement (I) is true but Statement (II) is false.