Govt. Exams
Entrance Exams
Light intensity directly affects photosynthesis but has no effect on respiration, which occurs in both light and dark conditions.
Quantum yield represents the photosynthetic efficiency, defined as the number of CO2 molecules fixed per photon absorbed (typically 8-10 photons per CO2).
Guttation occurs through specialized pores called hydathodes located at the leaf margins, allowing liquid water to be exuded when root pressure exceeds transpiration.
Light reactions do not require CO2. CO2 is used in the dark reaction (Calvin cycle). Light reactions produce ATP, NADPH, and O2.
At compensation point, the rate of CO2 fixation in photosynthesis equals the rate of CO2 release in respiration, resulting in net zero gas exchange.
Plasmodesmata are cytoplasmic bridges allowing symplastic movement of water, minerals, and even macromolecules like proteins and RNA between adjacent cells.
Stomatal oscillation refers to the dynamic opening and closing of stomata in response to changing environmental conditions to maintain optimal gas exchange while reducing water loss.
Ethylene accumulates in leaf petioles during water stress, promoting abscission layer formation, leading to leaf shedding. ABA increases ethylene production.
Wilting occurs when transpiration rate exceeds the water absorption rate by roots, even with adequate soil water, due to environmental stress or damaged vascular tissue.
Turgor pressure in sieve tubes is involved in phloem transport, not xylem transport. Water transport in xylem is driven by root pressure, capillarity, and transpirational pull.
