Ecological importance of water. Thermal water properties. Physical laws of solutions: Vapor pressure, solution potential, and latent heat. Plant relations with soil physical properties: Apparent specific gravity, soil compactness, soil water regime, and soil temperature regime. Soil water replenishment of the roots. Mechanism of water absorption ,Factors affecting ET and technology of ET reduction. Direct measurement of ET: Depletion, lysimeter, and pan evaporation Effect of water stress on plant growth and yield.