Benefits Of Drought

Stress is an external factor that exerts a disadvantageous influence on the plant and is measured in relation to plant survival, crop yield and growth (biomass accumulation). The major abiotic stresses are drought, high salinity, cold and heat which reduce the survival, biomass production and yields of staple food crops up to 70% (Thakur et al. 2010).

Drought is a major agricultural menace reducing crop productivity and limiting the successful realization of land potential throughout the world and improving yield under drought is a major goal of plant breeding. Drought tolerance is a quantitative trait, with complex phenotype and genetic control. It has low heritability, high genotype x environment interaction. Due to presence of variation

According to John Cushman, Biochemistry Professor at the University of Nevada, Reno “Drought stress accounts for more production losses than all other factors combined”. Drought is not a stable phenomenon and available soil water changes with time within a season. It often starts as mild stress and may become severe with time and last for a long period. In some cases, drought develops early during the vegetative stage, while in other cases it develops later, towards crop maturity. The drought patterns are different between locations and years and it often does not develop at all during the growth season in areas with favorable rainfall (Izanloo et al., 2008). Differences in seasonal distribution of rainfall and severity of water limitation also vary substantially from season to season for a given location. Therefore, identification of common drought patterns and their likelihood of occurrence are important for the development of cultivars that are suited for the region concerned. The nature of drought is complex and it can be considered as a set of climatic pressures which can be produced by several phenomena such as: heat shock, water deficiency, low air humidity, high irradiance and salinity. Different combinations of these phenomena cause different types of drought,

TYPES OF DROUGHT

There are four types of drought

1. Meteorological drought: It is defined as the amount of dryness and the duration of the dry period. Atmospheric conditions that result in the deficiencies of precipitation change from area to area.

2. Physiological drought: A drought condition suffered by plants that occurs despite there being sufficient water in the soil. It may occur when the concentration of solutes in the soil water is equal to or higher than that in the root cells so water cannot enter the plant by osmosis. This situation may be found in salt marshes and coastal mud flats. It also occurs during cold spells when there is an increase in the resistance of the root to water movement into the plant. Root resistance increases in response to low temperatures since the permeability of endodermal cells decreases rapidly below 5°C.

3. Hydrological Drought: It is associated with the effects of periods of precipitation shortages on water supply. Water in hydrologic storage systems such as reservoirs and rivers are often used for multiple purposes viz. agriculture. Competition for water in these storage systems escalates during and conflicts between water users increase