Impacts of Abiotic Stresses on Sorghum Physiology

Sorghum is an important coarse cereal grown in the arid and semiarid regions of the world for food and nutritional security. The resilience of sorghum crop to changes in climate can be improved through a better understanding of the physiological basis of abiotic stress tolerance or susceptibility. Among the various abiotic stresses that limit sorghum production, drought and temperature stress are of foremost importance. Apart from this, flooding, low-temperature, and salinity stress also affect sorghum productivity. Severity of stress is greater if these stresses occur during critical stages of crop growth and development. The primary effects of drought stress are decrease in tissue water content. Similarly, for salinity stress, the major effect is an alteration in tissue water content and ionic imbalance. The membranes are the primary site of action for temperature extremes. Among the various growth stages, reproductive stages, namely, gametes development and flowering, are most sensitive to drought, flooding, high-temperature, and low-temperature stress. Seedling emergence, early vegetative stages, and flowering are sensitive to salinity stress. Abiotic stress decreases photosynthesis and yields through decreases in green leaf area duration, radiation capture, decreased carbon partitioning, lower seed-set and grain numbers, and decreased individual grain weight. The decreased seed-set percentage is associated with loss of gametes (pollen and ovule) viability, embryo abortion, and embryo growth. The decrease in rate and duration of grain filling is responsible for lower individual grain weight. A better understanding of impacts on physiological processes, mechanisms, and traits associated with tolerance or susceptibility along with improved agronomic management practices will help in improving sorghum abiotic stress tolerance and management.