Elucidating the role of exogenous iron (Fe) in regulation of hydrogen sulphide (H2S) biosynthesis and its concomitant effect on seedling growth, pigment composition and antioxidative defense in NaCl stressed tomato seedlings

There is a paucity of information on the role of iron nutrition in regulating H2S-mediated salinity tolerance in plants. The present work implies exogenous Fe and Na2S (H2S-donor) for investigating the interactive effects of Fe and H2S in regulating seedling growth, osmolyte accumulation, chlorophyll accumulation and antioxidative defense under salinity stress. To achieve this, an experiment was set up with seeds of tomato (Solanum lycopersicum L. var. romeo) grown in presence of NaCl concentration (80 mM). Control seedlings were grown using half strength hoagland nutrient solution without NaCl. Exogenous Fe (100 mu M) and H2S was supplied in the form of Na2S (100 mu M) individually and in combination both in presence and absence of NaCl. Growth parameters like shoot length and root lengths were taken along with chlorophyll, osmolyte contents, enzymatic and non-enzymatic antioxidants as well as content of H2S and L-DES activity were also measured. Results demonstrated that exogenous Fe and H2S to an extent provide protection to tomato seedlings subjected to salt stress through prevention membrane damage, increased antioxidative defense and there was significant increase in L-DES activity that led to increased H2S content. Exogenous Fe and Na2S application in tomato seedlings under salt stress exhibited decrease in malondialdehyde content by 19% and 50% respectively and H2O2 by 13.7% and 16.8% respectively. Combined application of Fe and Na2S increased the levels of antioxidative enzyme activities including CAT (53.8%), POX (14%), SOD (58%) and APX (11.7%) was observed under salt stress. However, tomato seedlings supplemented with combined application of Fe and H2S showed decreased H2S content as well as lower L-DES activity. Simultaneously, combined application of Fe and H2S to salt stressed tomato seedlings however showed increased activity of some of the antioxidative enzymes deciphering positive role of this interaction of Fe and Na2S under the influence of salt stress.