Hydrogen Sulfide

Abstract

Hydrogen sulfide (H2S) has been considered as a phytotoxin for almost 300 years, having deleterious effects on plant growth and survival. However, in recent years, H2S has been added to nitric oxide (NO) and carbon monoxide (CO) as a newly categorized group of biologically active gases termed as gasotransmitters, due to its capacity to control a range of physiological responses. It is recognized that for H2S to have an effect on plants cells it has to be present in a high enough concentration. From the environment or from within are two main sources of H2S in plants. Natural sources include the discharge from volcanoes, coastal marine sediments, or anoxic soils such as found in marshland, while man-made sources include waste treatment installations, agricultural industries, and geothermal power plants. Likewise, intracellular sources of H2S in plants include the production by desulfhydrase enzymes. However, although at present there is no direct evidence that H2S acts as an endogenous regulator or signal molecule in plants, the induction of l-cysteine desulfhydrase upon pathogen attack, emission of H2S from plants exposed to SO2 injury, abiotic stress tolerance in plants supplied with endogenous H2S donor, and its involvement in guard cell signaling and root organogenesis, all suggest that this is indeed the case. Furthermore, endogenous and exogenous postharvest applications of H2S have been used for improvement of shelf life and quality attributes of food products. Recently and for future research, several research groups are focusing on H2S and its role as a signal in plants.