Hydrogen sulfide implications on easing NaCl induced toxicity in eggplant and tomato seedlings

In the present study, the role of hydrogen sulfide (H₂S) in alleviating NaCl (20 mM) induced toxicity on growth, photosynthetic pigments and photochemistry of PS II, and impact on oxidative stress and antioxidant systems of eggplant and tomato was studied. To confirm the role of H₂S (donor sodium hydrogen sulphide (NaHS; 40 μM)) under stress, H₂S scavenger; hypotaurine (HT; 200 μM) and inhibitor, propargylglycine (PAG; 100 μM) in combination with NaHS was added to the growth medium of NaCl stressed seedlings. The NaCl reduced the overall growth of the seedlings as the Na⁺ uptake was increased which led to removal of K⁺, thereby Na⁺/K⁺ homeostasis was disturbed. This condition caused severe impact on photosynthetic pigments and PS II photochemistry, thus significant decline in the values of fluorescence kinetics parameters such as F_v/F_m, F_V/F₀, φE₀, ѱ_0, PI_ABS except F₀/F_V and enhancement in energy flux parameters such as ABS/RC, TR₀/RC, ET₀/RC and DI₀/RC was obtained. Exogenous H₂S not only abolished the toxic symptoms in test seedlings but also completely alleviated the decline in growth in case of tomato seedlings. Reactive oxygen species accumulation was significantly declined in both the seedlings as evident by in vitro and in vivo analysis with the supplementation of NaHS, indicating appreciable recovery in membrane damage caused by NaCl toxicity. Antioxidative enzymes: SOD, POD, CAT and GST activities were further stimulated in response to H₂S (NaHS) supplementation to the stressed seedlings, thus maintaining the redox homeostasis of cell and bringing the seedlings back to the healthy state. Moreover, the role of endogenous and exogenous H₂S was also justified using the scavenger of H₂S (HT; 200 μM) and inhibitor of enzymes of H₂S (PAG; 100 μM). Thus, present study emphasizes the role of NaHS as H₂S donor in alleviating NaCl stress in crops particularly vegetables tomato and eggplant, and may be considered as a part of important strategies to cope up with NaCl toxicity which is prevailing in natural field condition.