Plants are subjected to a variety of environmental stresses, which reduce and limit agricultural crop productivity. Environmental stresses that affect plants are of two types: biotic and abiotic stresses. Abiotic stress includes temperature, ultraviolet radiation, salinity, floods, drought, heavy metals, etc., which result in the loss of important crop plants globally, while biotic stress refers to damage caused by insects, herbivores, nematodes, fungi, bacteria, or weeds. Plants respond to all these environmental factors because they are fixed in a particular place. To cope with these stresses, a number of strategies have been developed by plants. They detect that the environmental stresses have been activated and then generate the necessary cellular responses.