Abstract
Nitric oxide (NO) has now gained significant place in plant science, mainly due to its properties (free radical, small size, no charge, short-lived, and highly diffusible across biological membranes) and multifunctional roles in plant growth, development, and regulation of remarkable spectrum of plant cellular mechanisms. In the last few years, the role of NO in tolerance of plants to abiotic stress has established much consideration. As it is evident from the present review, recent progress on NO potentiality in tolerance of plants to environmental stresses has been impressive. These investigations suggest that NO, itself, possesses antioxidant properties and might act as a signal in activating ROS-scavenging enzyme activities under abiotic stress. NO plays an important role in resistance to salt, drought, temperature (high and low), UV-B, and heavy metal stress. Rapidly increasing evidences indicate that NO is essentially involve in several physiological processes; however, there has been much disagreement regarding the mechanism(s) by which NO reduces abiotic stress.