Physiology of Low Temperature Stress in Rice (Oryza Sativa L.)-A Review

Rice is evolutionary a crop of tropical and subtropical habitat but also grown in many cold regions of the world in late spring to summer, it is most susceptible to chilling temperatures and experiences a greater yield loss. Indica rice are known to be more sensitive to photo-inhibition at chilling temperatures than Japonica rice. Low temperature during seed germination and flowering is most critical in reducing the crop yield of rice. The imbibition phase of germination is considered to be the most sensitive, which leads to the escape of solutes from the seeds. During flowering the damage is particularly significant during microspore genesis stage of the pollen by causing male sterility. Phase transition, free radical production and mistiming of ci read tan rhythm are reported to be the few mechanisms of chilling damage in warm climate plants including rice. However, rice plants may develop tolerance by naturally producing osmoprotectants as well as antioxidant systems. External application of these chemicals may also be helpful in protecting the rice plants from low temperature damage. Cultivation of tolerant genotypes is the best way to ascertain maximum possible yield in cold prone areas. Routine screening of rice genotypes is required either for direct introduction after assessing their phenotypic acceptability to the local conditions or for their use as donors for transferring cold tolerant characters into the high yielding varieties.