Although thiamine (THI) and hydrogen sulphide (H2S) both have widely been tested in the plant under stress conditions, cross talk between THI and H2S in the acquisition of cadmium (Cd) stress tolerance needs to be studied. So, an experiment was designed to study the participation of endogenous H2S in THI-induced tolerance to Cd stress in strawberry plants. A foliar spray solution containing THI (50 mg L-1) was sprayed once a week for 4 weeks to the foliage of strawberry plants under Cd stress (1.0 mM CdCl2). The plant dry weight, total chlorophyll, maximum efficiency of PSII (Fv/Fm), leaf potassium (K+) and calcium (Ca2+) as well as leaf water potential were significantly reduced, but the proline, ascorbate (AsA), glutathione (GSH), malondialdehyde (MDA), hydrogen peroxide (H2O2), electron leakage (EL) and leaf Cd as well as endogenous H2S and NO were increased by Cd stress. Application of THI alleviated the oxidative damage due to Cd stress and caused a further elevation in endogenous H2S and NO contents. Remarkably, THI-induced Cd stress tolerance was further improved by addition of sodium hydrosulfide (0.2 mM NaHS), a H2S donor. To get an insight whether or not H2S involved in THI-improved tolerance to Cd toxicity in strawberry plants, an H2S scavenger, hypotaurine (HT 0.1 mM), was supplied along with the THI and NaHS treatments. THI-improved tolerance to Cd stress was partly reversed by HT by reducing leaf H2S and NO to the level and above of these under Cd toxicity alone, respectively. The findings evidently showed that leaf H2S and NO together involved in induced tolerance to Cd toxicity by THI. This evidence was also proved by the partly increases in MDA and H2O2 and decreases in antioxidant defence enzymes such as superoxide dismutase, catalase and peroxidase as well as the plant biomass and partly enhanced leaf Cd content by exogenous applied HT along with THI.
Keywords: Antioxidant defence system; Cadmium toxicity; Hydrogen sulphide; Strawberry; Thiamine.