Impact of heat stress on the physiology of different genotypes of rice (Oryza sativa L.) provides information on how heat stress affects the rice crop's physiology. It also includes information on the many enzymes and proteins involved during heat stress in rice crop. Heat stress is one of the most important determinants of crop seasonal growth and geographic distribution. Global warming has become a concern that cannot be disregarded as a result of population increase and industrial development. It is a huge challenge for the researcher to develop heat stress tolerant genotypes in the near future. This book describes how morphplogical parameters such as tiller number, leaf area, leaf dry weight, Specific leaf weight (SLW), Specific leaf area (SLA), stem dry weight, panicle dry weight, grain yield, thousand grain weight and spikelet fertility sterility, total dry weight and biochemical and physiological parameters such as Membrane stability Index, chlorophyll content, chlorophyllfluorescence, proline content, Superoxide dismutase (SOD), Catalase (CAT), Peroxidase (POD), amylose content, protein content, affected in different rice genotypes at anthesis.