**3.2 Dehydration avoidance**

It is the ability of a plant to retain a relatively higher level of hydration under conditions of soil or atmospheric water stress. Dehydration avoidance can be achieved either by reducing transpiration (water savers) or increased water uptake (water spenders). The following plant characteristics are responsible for dehydration avoidance. i) Reduced transpiration by closure of their stomata in water saving xerophytic species in response to water deficit well before wilting. In less irrigate plants, stomata possibly will remain open during morning hours and close as solar radiation increases. In CAM plants stomata closes during the night, when CO2 is fixed by them. ii) Osmotic adjustment is an important mechanism positively affects growth and yield under stress. iii) Increased concentrations of Abscisic acid a stress hormone plays an important role in water stress avoidance by effecting stomata closure, reduction in leaf expansion and promotion of root growth.

Many of stress responsive genes encodes such proteins e.g., dehydrin, osmotin, Lea proteins etc. also produced in response to ABA; genes encoding such proteins are called ABA responsive (ABAR) genes. iv) Deposition of wax within and over the cuticle reduces transpiration during water stress. v) Leaf characteristics like leaf pubescence, erect leaf angle, leaf rolling etc. vi) increased water uptake by deep root system.
