Govt Exams
PSII catalyzes photolysis of water at the oxygen-evolving complex, transferring electrons to plastoquinone in the thylakoid membrane.
Non-cyclic photophosphorylation involves PSII and PSI, producing ATP, NADPH, and O₂ from water photolysis.
Ethylene (C₂H₄) is the ripening hormone that triggers color change, softening, and aroma development in climacteric fruits.
Transpiration creates negative pressure (tension) in xylem; water cohesion allows continuous columns to be pulled upward against gravity.
Etiolation is the adaptation to grow in darkness: shoots elongate, leaves remain pale (no chlorophyll), and seedlings appear yellowish.
In C4 photosynthesis, CO₂ combines with phosphoenolpyruvate (PEP) to form oxaloacetate (4-carbon), catalyzed by PEP carboxylase.
Stomatal conductance (gs) is the rate of gas diffusion through stomata, dependent on aperture width and inversely on distance (g = A/L).
Osmotically active solutes like glucose, sucrose, malate, and K⁺ ions accumulate in vacuoles to maintain turgor pressure and cell rigidity.
Guttation is the exudation of xylem sap through hydathodes, caused by positive root pressure, especially in early morning when transpiration is low.
Quantum yield is the ratio of CO₂ fixed to photons absorbed, typically 0.05-0.1 (5-10 CO₂ per 100 photons).