▪Transpiration is the process by which water vapour leaver the living plant body and enters the atmosphere.
▪It involves continuous movement of water from the soil into roots, through the stem and cut through the leaves to the atmosphere.
▪The process include cuticular transpiration or direct evaporation in to the atmosphere from moist membranes through the cuticle, and stomatal transpiration or outward diffusion into the atmosphere through the stomata and lenticels vapour previously evaporated from imbibed membranes, into intracellular space within the plant.
▪Transpiration is an evaporation process. However, unlike evaporation from a water surface, plant structure and stomata behavior in conjunction with the physical principles governing evaporation modify transpiration.
▪The loss of water through transpiration is governed by temperature, humidity, wind velocity, moisture content in the soil and inherent characteristic of the plant.
▪Since transpiration is a physiological process, which must continue, if the plant has to grow, the only way to save this loss is by growing such crops and their varieties whose transpiration co-efficient is low. Transpiration can be checked to some chemicals.
▪Transpiration produces energy gradient, which causes movement of water into through plants.
▪When rainfall is high and water-holding capacity of soil is less, the losses due percolation are very great. Such losses are very rapid particularly when the soils are sandy and porous. In heavy soils, percolation is low because of more water holding capacity.
▪Besides rapid percolation of water, there is also heavy loss of plant nutrients viz. Ca, Mg, S, K etc. resulting in soil becoming acidic.
▪Percolation losses are maximum in humid climate. When high rainfall is received, the loss of water through percolation is necessary otherwise, poor drainage conditions and water logging may develop in heavy soils.
▪ When water is in excess of water holding capacity of soils, it percolates through the soil due to gravity.