Physiological, biochemical and root exudate response of maize seedlings to hydrogen sulfide applications

The effects of hydrogen sulfide (H2S), released from the donor sodium hydrosulfide (NaHS), on maize seedlings grown hydroponically for 6 days were investigated. Plant biomass, malondialdehyde (MDA), hydrogen peroxide (H2O2), superoxide (O2•−) content, and root exudates (organic acids) were measured. Results showed that 100 and 200 µM NaHS is the most appropriate and suitable concentration for the growth and development of maize seedlings, without affecting the MDA and H2O2 contents but altering the O2•−. In addition, high concentrations of 500 and 1000 µM NaHS adversely affected these parameters compared with the control (CK). The pH of the root exudates declined under NaHS treatments. The organic acids in the root exudates, including fumaric, acetic, formic, and malic acids exhibited higher contents at 100 µM NaHS treatment, the lactic and citric acids were higher at both 100 and 200 µM NaHS. In contrast, oxalic acid was reduced at all NaHS concentrations compared with the CK. Low contents of all the organic acids analyzed were found under 500 and 1000 µM NaHS treatment. In conclusion, all the above parameters were affected by the application of NaHS, while higher NaHS concentration was toxic for maize seedlings.