Search

Main conclusion: Stomatal aperture in maize is not affected by exposure to a subtoxic concentration of atmospheric H2S. At least in maize, H2S, thus, is not a gaseous signal molecule that controls stomatal aperture. Sulfur is an indispensable element for the physiological functioning of plants with hydrogen sulfide (H2S) potentially acting as gasotransmitter in the regulation of stomatal aperture. It is often assumed that H2S is metabolized into cysteine to stimulate stomatal closure. To study the significance of H2S for the regulation of stomatal closure, maize was exposed to a subtoxic atmospheric H2S level in the presence or absence of a sulfate supply to the root. Similar to other plants, maize could use H2S as a sulfur source for growth. Whereas sulfate-deprived plants had a lower biomass than sulfate-sufficient plants, exposure to H2S alleviated this growth reduction. Shoot sulfate, glutathione, and cysteine levels were significantly higher in H2S-fumigated plants compared to non-fumigated plants. Nevertheless, this was not associated with changes in the leaf area, stomatal density, stomatal resistance, and transpiration rate of plants, meaning that H2S exposure did not affect the transpiration rate per stoma. Hence, it did not affect stomatal aperture, indicating that, at least in maize, H2S is not a gaseous signal molecule controlling this aperture. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is an air pollutant present at high levels in various regions. Plants actively take up H 2 S via the foliage, though the impact of the gas on the physiological functioning of plants is paradoxical. Whereas elevated H 2 S levels may be phytotoxic, H 2 S levels realistic for polluted areas can also significantly contribute to the sulfur requirement of the vegetation. Plants can even grow with H 2 S as sole sulfur source. There is no relation between the rate of H 2 S metabolism and the H 2 S susceptibility of a plant, which suggests that the metabolism of H 2 S does not contribute to the detoxification of absorbed sulfide. By contrast, there may be a strong relation between the rate of H 2 S metabolism and the rate of sulfate metabolism: foliar H 2 S 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 H 2 S 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.