Ecophysiology and responses of plants under drought

Abstract

Drought stress (DS) is the most prevalent abiotic stresses limiting crop productivity across the world. Plants have evolved various mechanisms to tolerate drought effects. Drought resistance in plants, viz. escape, avoidance, tolerance and recovery, is anchored in genetics and physiology. Some plants have evolved smaller leaves and reduced stomata to reduce transpiration, some develop erect plant leaves for greater interception of solar radiation while others can invest on root elongation to tap water from deeper layers of soil. These responses to drought are expressed through regulations of proteins critical to water transport, assimilate mobilization and gene expression. Accumulation of compatible solutes and phyto-protectants like osmolytes, and antioxidants, also plays a major role in drought tolerance. Various drought-related physiological traits such as osmotic adjustment, root architecture, stomata physiology, plant-water relations and levels of phytohormones like abscisic acid (ABA) have been used as maker to evaluate drought resistance in plants. Plant response to drought is complex and involving several genes, gene regulators, transcription factors and plant hormones. Genetic improvement through QTL and gene discovery in crops like rice and wheat for osmotic adjustment, root architecture, biomass and grain yield have been used to increased resistance of these crops through marker-assisted breeding and genetic engineering. However, the dynamic nature of drought and its interaction of other abiotic stresses particularly heat constantly endanger plant to become more vulnerable. Hence, developing crops with enhanced tolerance to combined drought and associated stresses will ensure broad resistance to DS. Therefore, understanding physiological and molecular basis of drought resistance in crops is critical in breeding for better drought-tolerant crops. Present review will summarize current research on physiological responses of plants under DS.