NO and H₂S Contribute to Crop Resilience against Atmospheric Stressors

Atmospheric stressors include a variety of pollutant gases such as CO₂, nitrous oxide (NOx), and sulfurous compounds which could have a natural origin or be generated by uncontrolled human activity. Nevertheless, other atmospheric elements including high and low temperatures, ozone (O₃), UV-B radiation, or acid rain among others can affect, at different levels, a large number of plant species, particularly those of agronomic interest. Paradoxically, both nitric oxide (NO) and hydrogen sulfide (H₂S), until recently were considered toxic since they are part of the polluting gases; however, at present, these molecules are part of the mechanism of response to multiple stresses since they exert signaling functions which usually have an associated stimulation of the enzymatic and non-enzymatic antioxidant systems. At present, these gasotransmitters are considered essential components of the defense against a wide range of environmental stresses including atmospheric ones. This review aims to provide an updated vision of the endogenous metabolism of NO and H₂S in plant cells and to deepen how the exogenous application of these compounds can contribute to crop resilience, particularly, against atmospheric stressors stimulating antioxidant systems.