Govt Exams
Transpiration creates negative pressure (tension) in xylem; water cohesion allows continuous columns to be pulled upward against gravity.
In C4 photosynthesis, CO₂ combines with phosphoenolpyruvate (PEP) to form oxaloacetate (4-carbon), catalyzed by PEP carboxylase.
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).
The casparian strip is a hydrophobic barrier of suberin and lignin in the endodermis that prevents apoplastic transport and regulates ion uptake.
Arbuscular mycorrhizal fungi increase plant access to phosphorus and micronutrients (Zn, Cu) through their extensive hyphal networks in soil.
The Warburg effect in plants refers to photorespiration, where high O₂ competes with CO₂ for Rubisco binding, reducing net photosynthesis.
Calcium pumps actively transport Ca²⁺ into vacuoles, serving as a calcium reservoir for second messenger signaling in plant cells.
Wood is composed of secondary xylem with thick-walled tracheids and vessel elements that provide mechanical support and water transport. Annual rings visible in wood represent secondary xylem produced by vascular cambium.