Photomorphogenesis refers to light-dependent development processes including light-mediated seed germination. Phytochrome is the photoreceptor involved. This is distinct from photoperiodism (flowering response to day length).

The reduction phase of Calvin cycle requires 3 ATP per CO2 fixed. NADPH requirement is 2 molecules per CO2. These are stoichiometric ratios essential for understanding photosynthetic efficiency.

2,4-D is a synthetic auxin widely used as a selective herbicide. Natural auxin is IAA (Indole-3-acetic acid). This is application-based knowledge relevant for agricultural science in UPSC.

The Casparian strip is a band of suberin (waterproof lipid polymer) that prevents passive transport across the endodermis, forcing minerals to undergo active transport. This ensures selective ion uptake - a key NCERT concept.

CO2 saturation point is where further increase in CO2 doesn't increase photosynthesis rate because other factors (like enzyme activity) become limiting. Compensation point is where photosynthesis equals respiration.

ABA is a stress hormone that accumulates during drought, regulating stomatal closure and promoting seed dormancy. It antagonizes gibberellins and cytokinins. This is crucial for understanding plant responses to environmental stress.

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.

Calcium pumps actively transport Ca²⁺ into vacuoles, serving as a calcium reservoir for second messenger signaling in plant cells.

The Warburg effect in plants refers to photorespiration, where high O₂ competes with CO₂ for Rubisco binding, reducing net photosynthesis.

Arbuscular mycorrhizal fungi increase plant access to phosphorus and micronutrients (Zn, Cu) through their extensive hyphal networks in soil.