Mechanisms of Drought Resistance

Abstract

For a period of dry weather to affect a plant community, the rainfall deficit must lead to a soil water deficit and ultimately to a plant water'deficit. The degree to which a rainfall deficit is translated into a soil water deficit depends on the rate of evaporation during the rain-free period, and on the physical and chemical characteristics of the soil. The degree to which a particular soil water deficit influences the plant again depends on the degree of aridity of the atmosphere. However, it also depends on a number of plant characteristics that influence water uptake by the plant, the rate of transpira- tion and the response of the plant to the water deficit so generated. It is the degree to which the plant can withstand the rainfall deficit that constitutes its drought resistance. The characteristics that enable it to survive and grow through a rainfall deficit and soil-water depletion are the subject of this book, and in this chapter drought resistance will be defined and a simple classification of the various mechanisms of drought resistance in plants will be presented.