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High salinity greatly impacts agriculture, particularly in tomato (Solanum lycopersicum), a crop that is a model to study this abiotic stress. This work investigated whether hydrogen sulfide (H2S) acts upstream or downstream of nitric oxide (NO) in the signaling cascade during tomato response to salt stress. An NO-donor incremented H2S levels by 12-18.9% while an H2S-donor yielded 10% more NO in roots. The NO accumulated in roots one-hour after NaCl treatment while H2S accumulation started two-hour later. The NO stimulated H2S accumulation in roots/leaves, but not the opposite (i.e H2S was unable to stimulate NO accumulation) two-hour post NaCl treatment. Also, NO accumulation was accompanied by an increment of transcript levels of genes that encode for H2S-synthesizing enzymes. Our results indicate that H2S acts downstream of NO in the mitigation of oxidative stress, which helps tomato plants to tolerate high salinity.

The predicted environmental changes may be detrimental to initial seedling growth, particularly the expected increase in air temperature. We therefore investigated the thermal limits for growth and development of Vriesea friburgensis and Alcantarea imperialis seedlings in the context of oxidative stress. The optimal temperatures for the growth of V. friburgensis and A. imperialis were 25 and 25–30 °C, respectively. Extreme temperatures (15, 30, or 35 °C) induced oxidative stress in both species with significant accumulation of hydrogen peroxide (H2O2) and nitric oxide (NO). Under oxidative stress, the amount of chlorophyll decreased in both species, more prominently in V. friburgensis, while carotenoid levels dramatically increased in A. imperialis. Notably, the activities of superoxide dismutase, catalase (CAT), and ascorbate peroxidase increased in A. imperialis at extreme temperatures. Similar results were observed for V. friburgensis; however, the activity of CAT remained unaffected regardless of temperature. Seedlings of A. imperialis survived at a wider range of temperatures than V. friburgensis, which had greater than 40% mortality when growing at 30 °C. Overall, precise control of cellular H2O2 and NO levels takes place during the establishment of A. imperialis seedlings, allowing the species to cope with relatively high temperatures. The thermal limits of the fundamental niches of the species investigated, determined based on the ability of seedlings to cope with oxidative stress, were distinct from the realized niches of these species. The results suggest that recruitment success is dependent on the ability of seedlings to handle extreme temperature-triggered oxidative stress, which limits the regeneration niche.

High salinity affects plants due to stimulation of osmotic stress. Cell signaling triggered by nitric oxide (NO) and hydrogen sulfide (H2S) activates a cascade of biochemical events that culminate in plant tolerance to abiotic and biotic stresses. For instance, the NO/H2S-stimulated biochemical events that occur in plants during response to high salinity include the control of reactive oxygen species, activation of antioxidant system, accumulation of osmoprotectants in cytosol, induction of K+ uptake and Na+ cell extrusion or its vacuolar compartmentation among others. This review is a compilation of what we have learned in the last 10 years about NO participation during cell signaling in response to high salinity as well as the role of H2S, a new player in the mechanism of plant tolerance to salt stress. The main sources of NO and H2S in plant cells is also discussed together with the evidence of interplay between both signaling molecules during response to stress.