Plant Physiology- ICAR JRF/SRF 2024

• Statement (I) is False: Chloroplasts are fully differentiated, highly active photosynthetic plastids; chromoplasts and gerontoplasts typically represent terminal, non-photosynthetic or degenerative plastid stages.
• Statement (II) is True: According to the Endosymbiotic Theory (Lynn Margulis), chloroplasts originated from ancestral photosynthetic cyanobacteria engulfed by early eukaryotic cells, retaining a circular genome, 70S ribosomes, and a double-membrane envelope.
• Conclusion: Statement (I) is false but Statement (II) is true.

Correct option: (4) Statement (I) is false but Statement ({I) is true.

• Richmond-Lang Effect (1957): Cytokinins significantly delay leaf senescence and retard chlorophyll degradation by maintaining protein synthesis, suppressing protease activity, and actively mobilizing nutrients to cytokinin-treated tissues.
• Roles of Other Hormones: Auxins promote apical dominance and rooting; gibberellins promote stem elongation and seed germination; ethylene and abscisic acid promote senescence and abscission.

Correct option: (3) Cytokinins

• Seed Coat Anatomy (Fabaceae): In leguminous seeds, the subepidermal layer of the outer integument (testa) differentiates into a distinct palisade layer of vertically elongated, thick-walled sclereids called palisade cells (also known as Malpighian cells or macrosclereids).
• Function: These lignified, tightly packed cells provide mechanical protection and, together with the cuticle, create a water-impermeable barrier responsible for physical seed coat dormancy (hardseededness).

Correct option: (3) Subepidermal layer