Transpiration

Water taken up by the roots ultimately reaches the leaves and is released into the atmosphere as vapour - a loss called transpiration - and the scale of this loss is genuinely large: under about 5% of all the water a plant absorbs is actually retained for growth and metabolic use, with the rest transpired away. Although transpiration resembles simple physical evaporation, it differs in being carried out through a living biological system, principally the stomata, and the volumes involved can be striking, ranging from a couple of litres a day for a modest corn plant up to several hundred litres a day for a large tree such as a date palm, as summarised in Ta …