Q.What is water potential? Write any four factors affecting water absorption in plants.
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Start your 14-day free trial to unlock the full solution →Water potential (ψ) is the potential energy of water per unit volume relative to pure free water at atmospheric pressure and the same temperature; water always moves from higher to lower water potential.
Water potential drives water movement; absorption depends on soil water, temperature, aeration and transpiration.
Water potential (ψ, measured in pressure units, e.g. MPa) is a measure of the free energy of water in a system compared to pure water at standard conditions; pure free water is arbitrarily assigned ψ = 0, and the presence of solutes, pressure and matric forces make a system's water potential more negative. Water always diffuses spontaneously from a region of higher (less negative) water potential to one of lower (more negative) water potential, which is why water moves from the soil solution into root cells whose cell sap has a more negative ψ. Several external factors affect the rate of this water absorption: (1) Availability of soil water — dry soil (low soil water potential) reduces absorption. (2) Soil temperature — very low temperatures increase the viscosity of water and protoplasm and reduce root metabolic activity, decreasing absorption; moderate warmth favours it. (3) Soil aeration — poorly aerated (waterlogged) soils reduce oxygen for root …
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