Plant Growth Regulators And Functions — a labelled NEET Biology diagram with a definitions lexicon.
Plant Growth Regulators and Functions Labelled parts: Plant growth regulators, Auxin, Gibberellin, Cytokinin, Ethylene, Abscisic acid (ABA), Phototropism, Apical dominance, Cell elongation, Stem elongation, Seed germination, Shoot initiation, Cell division, Stomatal closure, Seed dormancy, Fruit ripening, Leaf abscission, Senescence, Unripe, Turning, Ripe, Open Stoma, Closed Stoma, Water Stress. ABA is a phytohormone primarily involved in plant stress responses, particularly drought and salinity. It promotes stomatal closure and induces seed dormancy. FYI: ABA levels increase significantly in leaves under water stress, leading to the closure of stomata to conserve water. This is the directional growth movement of a plant part (like a shoot) in response to light. Shoots exhibit positive phototropism (growing towards light), while roots show negative phototropism. FYI: The differential distribution of auxin (IAA) is responsible for phototropism; light causes auxin to migrate to the shaded side, promoting cell elongation there. It is the state where a viable seed remains metabolically inactive and fails to germinate even when environmental conditions are favorable. This prevents germination until specific conditions are met. FYI: Dormancy can be broken by scarification (physical removal of seed coat) or by chemical treatments (e.g., soaking in warm water). Senescence is the genetically programmed process of aging and eventual death of plant organs (like leaves). It involves the controlled breakdown and recycling of cellular components. FYI: The breakdown of chlorophyll and the yellowing of leaves (chlorosis) is a visible symptom of senescence, allowing nutrients to be salvaged by the plant. It is the process of shedding leaves from the plant, typically triggered by seasonal changes or stress. This is controlled by the formation of an abscission layer at the base of the petiole. FYI: The formation of the abscission layer involves the degradation of cell walls and the sealing of vascular bundles, preventing water loss.