Atmospheric H₂S: Impact on Plant Functioning

Hydrogen sulfide (H₂S) is an air pollutant present at high levels in various regions. Plants actively take up H₂S via the foliage, though the impact of the gas on the physiological functioning of plants is paradoxical. Whereas elevated H₂S levels may be phytotoxic, H₂S levels realistic for polluted areas can also significantly contribute to the sulfur requirement of the vegetation. Plants can even grow with H₂S as sole sulfur source. There is no relation between the rate of H₂S metabolism and the H₂S susceptibility of a plant, which suggests that the metabolism of H₂S does not contribute to the detoxification of absorbed sulfide. By contrast, there may be a strong relation between the rate of H₂S metabolism and the rate of sulfate metabolism: foliar H₂S absorbance may downregulate the metabolism of sulfate, taken up by the root. Studies with plants from the Brassica genus clarified the background of this downregulation. Simultaneously, these studies illustrated that H₂S fumigation may be a useful tool for obtaining insight in the regulation of sulfur homeostasis and the (signal) functions of sulfur-containing compounds in plants.