Drought Tolerance

As drought stress becomes more severe, it becomes increasingly more difficult to avoid dehydration; and mechanisms that allow plants to withstand reduced water content (more negative water potentials) become increasingly important. Drought tolerance is defined as the ability of plants to continue to function at lowered tissue water potentials. Drought-tolerating mechanisms often involve the maintenance of turgor (by accumulation of solutes) and/or desiccation tolerance (by protoplasmic resistance) (Jones et al., 1981). “Desiccation tolerant” plants can recover from a fully air-dried state (Vicre et al., 2004). When dehydrated, these plants are in a metabolically dormant, or cryptobiotic, state. Mesophytic plants, including all crop plants,

Drought score is an alternative method to determine drought stress tolerance. Drought score of all the varieties was ranged between 2 to 4, which indicates their nature as moderately resistant variety to drought stress. Singh et al., (2013) showed the plants with higher drought leaf area or with a larger number of plants per pot showed higher drought score under water stress condition. The number of tiller was also associated with leaf rolling score, drought score and proline

The mechanism is developed by rapid phenological development, developmental plasticity and recombination of pre-assimilates to grain. Escape strategies rely on successful reproduction before the onset of severe stress (Chaves et al., 2003). Drought escape though early flowering is advantageous in environmental with terminal drought stress and where physical or chemical barriers inhibited root growth (Bidinger and witcombe, 1989). This mechanism involves rapid phenological development, developmental plasticity (variation in duration of growth period depending on the extent of water deficit) and remobilization of pre-anthesis assimilates to the grain (Turner, 1979). In drought-prone upland areas of eastern India and Bangladesh, drought escape is an important mechanism that allows rice to produce grain despite limited water availability (Khush et al., 1997; Bernier et al.,