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

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ORIGINAL ARTICLE

Atmospheric ­H2S exposure does not affect stomatal aperture in maize Ties Ausma1   · Jeffrey Mulder1 · Thomas R. Polman1 · Casper J. van der Kooi1   · Luit J. De Kok1  Received: 23 July 2020 / Accepted: 12 September 2020 © The Author(s) 2020

Abstract 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. Abstract  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 H ­ 2S is metabolized into cysteine to stimulate stomatal closure. To study the significance of H ­ 2S for the regulation of stomatal closure, maize was exposed to a subtoxic atmospheric H ­ 2S level in the presence or absence of a sulfate supply to the root. Similar to other plants, maize could use H ­ 2S 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, H ­ 2S is not a gaseous signal molecule controlling this aperture. Keywords  Stomata · Transpiration · Signal molecule · Gasotransmitter · Sulfur metabolism · Air pollution

Introduction Sulfur is an essential macronutrient for plants, which plants usually acquire as sulfate via the root (Hawkesford and De Kok 2006). After its uptake, sulfate is reduced via several intermediates to sulfide, which is subsequently incorporated in cysteine via the reaction of sulfide with O-acetylserine (OAS), catalyzed by the enzyme O-acetylserine(thiol)lyase (OAS-TL; Hawkesford and De Kok 2006). Cysteine functions as the precursor and reduced sulfur donor for the synthesis of other organic compounds. Communicated by Anastasios Melis. Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s0042​5-020-03463​-6) contains supplementary material, which is available to authorized users. * Ties Ausma [email protected] 1



Laboratory of Plant Physiology, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands

It is often assumed that sulfur-containing metabolites might modulate physiological processes in plants. Hydrogen sulfide (­ H2S) might act as endogenous gasotransmitter that affects plant development and stress tolerance (Sirko and Gotor 2007; Calderwood and Kopriva 2014; Maniou et al. 2014; Hancock 2018). Moreover, H ­ 2S might control the aperture of stomata (Lis