Physiological Response of Rice (Oryza sativa L.) Plant to Biotic and Abiotic Stress: Review

The response of rice plant to biotic and abiotic stresses is custom-tailored for the nature of stresses due to additive, negative or interactive effects of responses initiated by any of stresses. Rice plants sense environmental signals before being able to answer appropriately to abiotic and biotic stress. Chlorophyll pigment declines when rice plant faces water deficiency and harms potential of mesophyll cell to capably utilize carbon dioxide. Drought stress cause stomatal closure and limits gas exchange, reduces water content and results in wilting of the plant. Physiological features in net photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency and CO₂ concentration disrupted by deficiency of water. Drought stress tolerance achieved through operating hormone metabolism, photosynthesis, respiration and water relation of physiological processes. Salinity influences osmotic and ionic stress and salt stressed plants exhibit enhanced concentration of reactive oxygen. The effect of salinity on rice plant is initiated by osmotic ingress characterized by lowered osmotic potential followed by later ionic effect causing ionic toxicity. Among physiological response level of rice, mitochondria and chloroplast proves more vulnerable organisms than the rest. Rice genotypes response to heat stress varies with phonology which contains morphoanatomical and cellular to molecular level. High temperature above the threshold level with in a certain period causes physiological processes of rice plant such as stomata opening, photosynthesis, growth and reproductive stage. Increase in temperature will lead to more rapid development, increased reproductive potential and more generations of pests and pathogens in a season. Reduction in photosynthetic rate at a high level of root knot nematodes infestation observed due to damage of local tissue of the plant. Silicon has an essential role to offset biotic and abiotic stress faced by rice plant. Abscisic acid is major abiotic stress responsive phytohormone involved in response to drought, osmotic and salt stress, cold and high temperature specific response. The shoot and root growth of rice inhibited by existence of higher NaCl but application of silicon alleviated salt induced injury. Physiological traits of rice, parades extremely vulnerable to biotic and abiotic stress however, alarming stress tolerance hormonal and osmotic mechanism settled by the plant as well as application of silicon alleviated drawbacks. Improved plant reaction against pathogen infections and abiotic stresses has innovative product, the painstaking mechanism which modulates plant physiology through potentiation of host defense mechanisms.