Rice Responses and Tolerance to High Temperature

Climate change may increase storms, flooding and other harsh weather events and, thus, change geographical crop distribution, growing season and may also shorten the growth period. An approximately, 3–4°C increase in global mean temperature would decrease food productivity by altering various vital functions of plants. A rise in the optimum temperature (28/22°C) by about 1°C may led to a 10% decrease in rice yield. High temperatures (above 30°C) at lower altitudes in tropical regions and low temperatures (below 15°C) in the temperate regions adversely affect rice yield. Rice yield is estimated to shrink by 41% by the end of the 21st century because of heat stress (HS) through spikelet degradation, floral sterility, protein denaturation, loss of membrane integrity, enzyme inactivation, production of toxic compounds and reactive oxygen species. HS may disturb photosynthesis and respiration by altering the movement of water, ions and organic solutes across the cell. It also adversely affects physiological parameters (chlorophyll content, net photosynthetic rate, and RuBP carboxylase activity). High night temperature is comparatively more deleterious than high day temperature for rice. In rice heat tolerance (HT) is majorly comprises of escape or avoidance. Heat shock proteins and other stabilizing features play a vital role in rice HT by improving photosynthesis, partitioning of assimilate, nutrient and water use efficiency and membrane thermal stability. Similarly, the cyclic electron transport may also perform a vital role in rice thermo-tolerance. Based on available literature there is a need for more accurate knowledge and new heat-tolerant cultivars to minimize the adverse effects of climate change on rice quality and productivity.