Explain factors affecting water absorption.

Answer: Factors affecting absorption of water by roots:

1. Available soil water: only capillary water is available to plants; absorption falls as soil water decreases (and stops at wilting coefficient).
2. Concentration of soil solution: a high solute concentration (saline soil) lowers the water potential of soil and decreases absorption; it may even cause exosmosis.
3. Soil temperature: absorption is maximum at about 20–30 °C; low temperature increases viscosity of water and decreases permeability and root activity.
4. Soil aeration: good aeration provides O₂ for root respiration (needed for active absorption); waterlogged, poorly aerated soil reduces absorption.
5. Rate of transpiration: a high transpiration rate creates a pull and increases (passive) absorption.