Factors Affecting Water Absorption:
1. Soil water: Availability of water in the soil directly influences the rate of absorption by the root.
2. Transpiration: More the rate of transpiration more is the rate of absorption. Transpiration directly influences the passive absorption process. Because it creates a suction force in the xylem vessel which extends up to root hairs.
3. Soil Air: Soil space remains filled up with air. Roots respire more during active absorption which requires metabolic energy. In the absence of O2 absorption slows down because the energy required for the purpose is not released.
4. Soil Temperature: An optimum temperature is necessary for any kind of metabolic activity. Absorption being a metabolic activity suffers if the temperature is less than 20°C. The soil becomes Physiologically dry for plants if the temperature is not within 20 – 40°C.
5. Soil Solution: If the soil solution becomes more concentrated due to the presence of soluble minerals, the rate of absorption becomes slow. This is because the OP of soil solution becomes more than the OP of the cell sap.
6. Root growth: The absorption of water also depends upon the growth of the root system. Soils that are hard, sandy, rocky or water-logged do not favour proper root growth. Roots when can move deeper into the soil layer or extend far away from the plant can absorb more water. An extensive root system always favours better absorption.
7. Wilting: Wilting is a phenomenon of water deficit in plants. Wilting causes shrinkage in the volume of water in the plant cells which leads to loss of turgidity. The loss of turgidity causes drooping of leaves or young stems. Wilting may not be visible externally. This is called incipient wilting. During hot days herbaceous plants show temporary wilting due to excessive transpiration. During night such plants regain their turgidity. Permanent wilting results from non availability of water for absorption for many days. The Turgidity of such plants cannot be restored.