Effect of selenium on salt signaling and tolerance in Salicornia iranica

The growth of euhalophytes is stimulated in low salt concentrations. However, the signaling events leading to such a positive response to salt have not been investigated so far. To our knowledge, no study has explored the ameliorative effect of selenium (Se) under salinity conditions in halophytes, including euhalophytes. In this research, we studied biomass production, signaling events, and biochemical markers of growth in Salicornia iranica under control, salinity (100 mM as NaCl), and Se (10 µM as Na2SeO4) for four weeks either as single treatments or in combination. Based on the obtained results, salt and Se improved plants’ growth by 2.5 and 1.5-folds, respectively. The highest growth (with up to 4-fold higher biomass compared with control plants) was achieved under the combination of both treatments. According to the data from temporal analyses, the salt treatment declined the leaf nitric oxide (NO) and hydrogen peroxide (H2O2) levels, suggesting a down-regulation of defense responses under optimum salt concentrations in this species. Also, Se treatment alone or in combination with salt decreased the H2O2 level. However, similar to salt, it increased hydrogen sulfide levels in the shoot and roots. The activity of antioxidant enzymes suggested catalase as the responsible enzymatic mechanism for the observed H2O2 signal. Both treatments and their combination decreased the content of malondialdehyde and methylglyoxal, attenuated defense response, and enhanced carbon and nitrogen assimilation. Our data showed a synergistic interaction between salt and Se and suggested using Se to improve plants’ productivity and their quality for edible and medicinal purposes.