Atmospheric H(2)S exposure does not affect stomatal aperture in maize

MAIN CONCLUSION: Stomatal aperture in maize is not affected by exposure to a subtoxic concentration of atmospheric H(2)S. At least in maize, H(2)S, thus, is not a gaseous signal molecule that controls stomatal aperture. ABSTRACT: Sulfur is an indispensable element for the physiological functioning of plants with hydrogen sulfide (H(2)S) potentially acting as gasotransmitter in the regulation of stomatal aperture. It is often assumed that H(2)S is metabolized into cysteine to stimulate stomatal closure. To study the significance of H(2)S for the regulation of stomatal closure, maize was exposed to a subtoxic atmospheric H(2)S level in the presence or absence of a sulfate supply to the root. Similar to other plants, maize could use H(2)S as a sulfur source for growth. Whereas sulfate-deprived plants had a lower biomass than sulfate-sufficient plants, exposure to H(2)S alleviated this growth reduction. Shoot sulfate, glutathione, and cysteine levels were significantly higher in H(2)S-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 H(2)S exposure did not affect the transpiration rate per stoma. Hence, it did not affect stomatal aperture, indicating that, at least in maize, H(2)S is not a gaseous signal molecule controlling this aperture. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00425-020-03463-6) contains supplementary material, which is available to authorized users.