Question

Why does transpiration call for a critical evil in plants

Answer 1

The loss of water in the form of vapour from aerial parts of the plant is called transpiration. Transpiration is said to be a necessary evil because it is an inevitable, but potentially harmful, consequence of the existence of wet cell surfaces form which evaporation occurs. Loss of water from the plant results wilting, serious desiccation and often death of a plant if a condition of drought is experienced. There is strong evidence that even mild water stress results in reduced growth rate and in crops to economic losses through reduction of yield.
Despite its apparent inevitability, transpiration is also of great significance for the plant.
Water is conducted in most tall plants due to transpiration pull.
Minerals dissolved in water are distributed throughout plant body by transpiration stream.
Evaporation of water from the exposed surface of cells of leaves has cooling effect on plant. Wet surface of leaf cells allow gaseous exchange.Transpiration affects indirectly the processes of respiration and photosynthesis