How nitric oxide donors can protect plants in a changing environment: what we know so far and perspectives

The free radical nitric oxide (NO) plays important roles in plant growth and defense. Owing to its small size and lipophilicity, NO acts as a crucial signaling molecule in plants, crossing cell membranes and enhancing cell communication. Indeed, NO donors have been shown to modulate a variety of physiological processes, such as plant greening, seed germination, iron homeostasis and mitochondrial respiration. Recently, several papers have reported the protective actions upon application of low molecular weight NO donors in plants under abiotic stress. Exogenous NO is able to improve plant tolerance to several abiotic stresses, such as drought, salinity, metal toxicity, and extreme temperatures. This protection is assigned to the NO-mediated redox signaling in plants, which involves interplay with reactive oxygen species and modulation of gene expression and protein function. This review reports and discusses the recent advantages, pitfalls, challenges, and perspectives in the applications of low molecular weight NO donors in plants under abiotic stress. The combination of nanotechnology and NO donors as an efficient approach to protect plants under challenging environments is also discussed.