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NO and H2S effects on stomata aperture in pepper (Capsicum annuum L.) under salt stress and recovery conditions

High salinity in soil, substrate or nutrient solution reduces the availability of free water resulting in cell protoplasm dehydration, oxidative stress and overall disruption of plant physiological processes. A good water supply to leaf epidermal cells is crucial for proper stomata movements, thus an important physiological adaptation of plants to salt stress includes a modulation of guard cells function. As opposite to salt tolerant halophytes, most agricultural plants are glycophytes with an increased susceptibility to Na+ ions, which stimulate stomata opening and affect transpiration regulatory mechanisms. Here, leaves of a typical glycophyte i.e. pepper plant (Capsicum annuum L.) were treated with hydrogen sulfide (H2S) donors (NaSH, GYY4137), a nitric oxide (NO) donor (SNP) and their combinations in vitro, with the aim to establish the effects of H2S and NO on stomata movements during salt stress and a recovery period. As expected, in unstressed plants, both the H2S donors stimulated stomata opening, with a pronounced effect of NaSH. In combined treatments the effects of NO and H2S were mutually neutralized, and the apertures were similar to control (untreated epidermal peels). In plants exposed to 150 mM NaCl for three days, SNP closed the stomata while both H2S donors led to stomata opening, again with the pronounced effect of NaSH. Combinations of SNP and H2S donors had similar effects on stomata aperture as observed in unstressed plants. After a recovery period, treatment with SNP caused stomata closure and the effect of H2S donors alone was ablated. Although the effect of NO was more suppressed when in the combination with GYY4137. In general, salt stress stimulated pepper stomata to open, which continues even during a recovery phase. These results suggest that NO and H2S interact during and after salt stress in pepper, with different H2S donors efficacy seen in recovery stage. As water availability and other ecological conditions such as CO2 concentration, temperature and irradiation affect stomatal movements, H2S and NO donors could be used as potential regulators of plant transpiration rate, especially in salt sensitive plants. Further research should give an insight into how these two gasotransmitters interact in multiple stress conditions and other agricultural species.

nitric oxide ; hydrogen sulfide ; stomata ; cell signaling ; salt stress

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