The role of nitric oxide in systemic responses of plants

Plants are exposed to various biotic stressors during their life which often leads to a localized cell death termed as hypersensitive response (HR) and induces systemic responses in their distal organs from the infected ones which often promotes the development of systemic acquired resistance (SAR) against secondary pathogen infection. These processes are regulated by various phytohormones, defense-related molecules, and free radicals such as reactive oxygen species (ROS) and nitric oxide (NO). NO acts together with these compounds regulating HR and rapid systemic defense responses of plants such as SAR, as well as taking part in the induced systemic resistance (ISR). In this chapter, the production and transport of NO and its signaling functions are summarized and shown in the acquired- or induced-, rapid- and long-term systemic responses of plants.