Essential Vocabulary for NEET PP-04
| Term | Definition |
|---|---|
| Water potential (Ψw) | Free energy of water per unit volume; Ψw = Ψs + Ψp |
| Solute potential (Ψs) | Reduction in water potential due to dissolved solutes; always ≤ 0 |
| Pressure potential (Ψp) | Component of Ψw due to pressure; positive in turgid cells |
| Osmosis | Movement of water from high Ψw to low Ψw across semipermeable membrane |
| Plasmolysis | Shrinkage of protoplast from cell wall when placed in hypertonic solution |
| Incipient plasmolysis | State where Ψp = 0; threshold of plasmolysis |
| Imbibition | Adsorption of water by hydrophilic colloids without forming solution |
| Apoplast | Non-living continuum of cell walls and intercellular spaces |
| Symplast | Living continuum of cytoplasm connected by plasmodesmata |
| Plasmodesmata | Cytoplasmic channels connecting adjacent plant cells through cell walls |
| Casparian strip | Band of suberin in endodermal cell radial/transverse walls; blocks apoplast |
| Endodermis | Innermost cortex layer in root; location of Casparian strip |
| Root pressure | Positive hydrostatic pressure in root xylem from osmotic water influx |
| Guttation | Exudation of liquid water droplets through hydathodes; driven by root pressure |
| Hydathodes | Specialised pores at leaf tips/margins through which guttation occurs |
| Cohesion-tension theory | Dixon & Joly; transpiration pull + cohesion maintain continuous xylem column |
| Transpiration | Loss of water vapour from aerial plant parts; mainly through stomata |
| Stomatal transpiration | 90-95% of total; regulated by guard cell pump and ABA |
| Cuticular transpiration | 5-10%; through waxy cuticle; largely unregulated |
| Lenticular transpiration | <1%; through lenticels in bark; unregulated |
| Guard cells | Paired cells flanking stomatal pore; regulate aperture via and turgor |
| ABA (Abscisic acid) | "Stress hormone"; signals stomatal closure under drought |
| Macronutrients | 9 essential elements required in large quantities: C,H,O,N,P,K,Ca,Mg,S |
| Micronutrients | 8 essential elements required in trace amounts: Fe,Mn,Zn,Cu,Mo,B,Cl,Ni |
| Essentiality criteria | Arnon & Stout: required for life, non-substitutable, directly metabolic |
| Chlorosis | Yellowing of leaves due to chlorophyll deficiency/failure |
| Necrosis | Cell/tissue death; brown/black discolouration |
| Nitrogenase | Mo-Fe enzyme that fixes → ; requires 16 ATP, anaerobic |
| Leghemoglobin | -binding protein in legume root nodules; creates microaerobic environment |
| Heterocysts | Thick-walled cells in Anabaena/Nostoc lacking PS II; sites of fixation |
| Nitrification | Oxidation of → (Nitrosomonas) → (Nitrobacter) |
| Denitrification | Reduction of → by Pseudomonas/Thiobacillus |
| Ammonification | Decomposition of organic N → by saprophytic bacteria/fungi |
| Nitrogen fixation | Reduction of atmospheric → by nitrogenase |
| Cavitation | Breaking of water column in xylem due to air bubble formation |
| Whiptail disease | Mo deficiency disease in cauliflower (leaves reduced to midrib) |
| Little leaf disease | Zn deficiency; reduced auxin synthesis impairs leaf elongation |
| Hydroponics | Growing plants in controlled nutrient solutions; used to determine essential elements |