Mention any four factors affecting water absorption.

Answer: Factors affecting water absorption by roots:

1. Available soil water: capillary water is readily absorbed; too little (or waterlogging) reduces absorption.
2. Soil temperature: low temperature increases viscosity of water and reduces permeability and root activity, so absorption falls.
3. Soil aeration: poor aeration reduces root respiration and active absorption.
4. Concentration of soil solution: a high solute concentration (saline soil) lowers the water potential gradient and reduces absorption.
5. Rate of transpiration also affects passive absorption.