NEET High-Priority Comparison
| Feature | Guttation | Transpiration |
|---|---|---|
| Form of water | Liquid droplets | Water vapour |
| Exit structure | Hydathodes | Stomata (90-95%) |
| Driving force | Root pressure (positive) | Cohesion-tension pull (negative) |
| Time of occurrence | Night / Early morning | Daytime (peak afternoon) |
| When it occurs | Low transpiration, high root pressure | High temperature, sunlight |
| Reversibility | Stops when transpiration begins | Continuous during daytime |
| Water composition | Contains dissolved minerals | Pure water vapour |
| Clinical significance | Indicates root pressure active | Indicates active water transport |
NEET TRAP: Both involve water loss from leaves. Key discriminator: Guttation = LIQUID through HYDATHODES = NIGHT = ROOT PRESSURE. Transpiration = VAPOUR through STOMATA = DAY = COHESION-TENSION.
Diagrams:
Hydathode — Cross Section Hydathode Pore (water exits here) (intercellular spaces) Epithem cells (loosely packed) Xylem Phloem Vascular bundle end Lower Epidermis Water exits as liquid droplets (guttation) under root pressureHydathodes: permanently open pores at leaf tips and margins through which guttation droplets emerge. Unlike stomata, hydathodes cannot close.