Abstract: We studied the effect of exogenous NaHS on seed germination and physiological characteristics of Cucurbita ficifolia under NaHCO₃ stress. NaHCO₃ stress inhibited the germination rate, hypocotyl length and radicle length and decreased the soluble sugar content as well as activities of α-amylase, β-amylase, superoxide dismutase (SOD) and peroxidase (POD). While, exogenous NaHS treatment significantly increased hypocotyl length and radicle length as well as soluble sugar content. Moreover, exogenous NaHS treatment increased the activities of α-amylase, β-amylase, SOD and POD and decreased the accumulation of malondialdehyde (MDA). Treatment with other salts including Na₂S, Na₂SO₄, NaHSO₄ and NaHSO₃ had no effect on germination rate under NaHCO₃ stress. Na₂HPO₄-NaH₂PO₄ buffer (pH 5.8–7.8) did not promote seed germination under NaHCO₃ stress as did NaHS treatment could be concluded that exogenous NaHS effectively alleviated the toxic effects of NaHCO₃ stress on seed germination, and the function of NaHS was attributed to H₂S.

Key words: Cucurbita ficifolia, NaHS, NaHCO₃ stress, seed germination, physiological characteristics