Nitric oxide (NO) is a gaseous diatomic radical with a wide variety of physiological and pathological implications in animal, plant and microbes. NO reacts directly with metal complexes and other radicals and indirectly as a reactive nitrogen oxide species with DNA, proteins, and lipids. In animals, NO is a signal transduction element that is synthesized by nitric oxide synthase (NOS) enzyme from L-arginine that functions in many tissues and interacts with multiple target compounds in neurotransmission, vascular smooth muscle relaxation, and platelet inhibition. In plants; NO is synthesized enzymatically by NOS like enzyme, nitrate reductase, nitrite reductase etc. and also by non-enzymatically. NO play a diverse role in plant system including plant growth, stomatal movement, iron homeostasis, protection against biotic and abiotic stresses, senescence etc.
Key words: Nitric oxide (NO), nitric oxide synthase (NOS), nitrate reductase (NR), reactive oxygen species (ROS), c-GMP, L-Arginine.
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