Abstract: Hydrogen sulfide(H₂S) is a new gas signal molecule and calcium(Ca²⁺) is an important second messenger. Both play important roles in plant adversity response, respectively. The experiment was conducted to clarify the role of cytosolic Ca²⁺ in germination of crop seed promoted by exogenous H₂S under saline-alkali stress. Naked oat(Avena nude) was selected as experimental material which was cultured in petri dishes in incubator. Mixed saline-alkaline solution(NaCl:Na₂SO₄:Na₂CO₃:NaHCO₃ with the mole ratio of 12:8:1:9) was used to simulate the saline-alkaline stress of naked oat growing areas in Gansu Province, extracellular Ca²⁺ chelator ethylene glycol-bis-(2-aminoethylether)-N, N, N', N'-tetraacetic acid(EGTA), plasma membrane Ca²⁺ channel blocker lanthanum chloride(LaCl₃), tonoplast Ca²⁺ release inhibitor ruthenium red(RR), and endoplasmic reticulum calcium pump blocker thapsigargin(Thaps) were combined with sodium hydrosulfide(NaHS, a donor of H₂S), respectively, and distilled water treatments were set as control. Seven germination indexes including germination potential, germination rate, germination index, vigor index, average germination speeds, radicle length, and plantule length of naked oat under control, saline-alkaline stress and co-treatments were determined. The membership function analysis was performed to comprehensively evaluate the effect of cytosolic Ca²⁺ on seed germination of naked oat enhanced by H₂S under saline-alkali stress. The germination potential, germination rate, germination index, vigor index, average germination rate, radicle length and plantule length of naked oat seeds decreased significantly with the increase of saline-alkaline concentration. Compared with the control, the 15-75 mmol·L^-1 salt-alkaline stresses resulted in a significant decrease in the membership function comprehensive evaluation value D, D value decreased by 73.1% under 30 mmol·L^-1 saline-alkali stress. The 100-1 000 μmol·L^-1 NaHS increased the D value to varying degrees, and 100 μmol·L^-1 NaHS had the most significant mitigation effect on the decrease of D value under 30 mmol·L^-1 salt-alkaline stress. This mitigation effect of NaHS was weakened by adding EGTA, LaCl₃ and RR, respectively; however, Thaps had no significant effect on the alleviating effect of NaHS to the decrease of D value under 30 mmol·L^-1 salt-alkaline stress. These results show that Ca²⁺ involved signal transduction in promoting of naked oat seed germination induced by H₂S under saline-alkali stress, and cytosolic Ca²⁺ mainly comes from the influx of extracellular Ca²⁺ and the release of Ca²⁺ in vacuoles.

Key words: H₂S, Ca²⁺, naked oat, saline-alkali stress, seed germination