What are the role of environmental factors on transpiration and how plants defend themselves against water loss? What are the role of environmental factors on transpiration and how plants defend themselves against water loss? Solution Role of environmental factors on transpiration 1. Relative humidity The loss of water vapour from stomata occurs by simple diffusion. When the atmosphere is very humid, the rate of loss of water vapour is lowered. Wind: When the wind velocity is high, rate of transpiration also increases. Temperature: Warm air hold more water vapour so the rate of loss of water increases with increase in temperature. Light: Opening and closing of stomata is regulated by light. More light result in high degree of transpiration. Soil water content: When there is less water content in the soil , the leaf droops / get dehydrated making the stomata to close resulting in less rate of transpiration. Carbon dioxide concentration When the concentration is high, stomata closes resulting in low rate of transpiration and vice versa. Plants defense mechanism against water loss Plants require water for it\'s survival. So it will have to regulate water loss ( especially during drought) . Several leaf adaptations help to combat water loss. Leaf arrangements play important role, transversely arranged leaves loss more water than perpendicularly arranged ones. Other anatomical features of the leaves such as sunken/vestigial stomata and closely arranged mesophyll cells reduces transpiration. Presence of hair, cuticle(waxy) , gums, mucilage etc on leaf surface help reducing transpiration. During drought, plant hormone abscisic acid play an important role by closing the stomata reducing water loss..