Ecophysiology of plants in dry environments

Abstract

Drought is a meteorological term which indicates a long period when there is not enough rain for the successful growing of crops or replenishment of water supplies. The expression water stress is frequently used to indicate the complex series of effects that are triggered in plants by drought. The term drought stress is more appropriate to specify when the stress status occurs only over a long period of time. However, because it is often difficult to separate the two phenomena, the definitions of water stress, drought stress and water deficit are frequently used interchangeably. Drought leads to water deficit in the soil and plant tissues, which in turn alters physiological processes and can have ultimate consequences for growth, development and survival of plants. Among the many biochemical and developmental processes that are affected by water stress, decrease of photosynthesis (Bradford and Hsiao, 1982; Flore and Lakso, 1989; Hsiao, 1973), changes in water relations (Brough et al., 1986; Olien and Lakso, 1986), reduction of both cell division and expansion (Hsiao and Acevedo, 1974), abscisic acid (ABA) synthesis (Davies and Zhang, 1991; Zeevaart and Creelman, 1988), and accumulation of sugars (Wang et al., 1995; Wang and Stutte, 1992) play a fundamental role in reducing productivity.