Exogenous H₂S regulates growth, and antioxidative defense in tomato seedings in a concentration dependent manner...

H₂S is a lipophilic gaseous molecule with the characteristic pungent "rotten egg" odour. Studies have shown that H₂S at lower concentrations acts as a gasotransmitter, providing evidence for its crucial role in plant growth, development and stress responses. The present work underlies the effects of moderate and high concentrations of NaCl stress and two concentrations of NaHS (H₂S donor) on certain metabolic signatures of tomato seedlings. In this study, tomato seedlings were grown under different NaCl concentrations (0 mM, 40 mM, 80 mM and 120 mM) and three concentrations of H₂S, i.e. T0 (0 µM), T1 (25 µM) and T2 (100 µM) were applied exogenously. The results showed a reduction in MDA content, electrolytic leakage, Na⁺/K⁺ ratio, and proline content in tomato seedlings with exogenous application of H₂S under NaCl stress. On the contrary, exogenous H₂S application at T2 concentration increased chlorophyll content, RWC, endogenous H₂S content, L-DES activity and ascorbate content under 80 mM NaCl stress. Concomitantly, exogenous H₂S treatment, particularly at T2 concentration, upregulated the antioxidative enzyme activity like glutathione reductase (GR), catalase (CAT), ascorbate peroxidase (APOD), peroxidase (POD) and superoxide dismutase (SOD) in NaCl-treated tomato seedlings. These results indicate that exogenous H₂S application, especially at T2 concentration, imparts a higher amount of alleviation in salt-stressed tomato seedlings grown under 80 mM NaCl. Thus, a concentration-dependent interaction of NaCl stress and H₂S signaling appears to be mediated through long-distance signaling in tomato seedlings.