Protective role of hydrogen sulfide （H2S） on seed germination and seedling growth was studied in wheat （Triticum） seeds subjected to aluminum （Al3＋） stress. We show that germination and seedling growth of wheat is inhibited by high concentrations of AICI3. At 30 mmol/L AICI3 germination is reduced by about 50% and seedling growth is more dramatically inhibited by this treatment. Pre-incubation of wheat seeds in the H2S donor NaHS alleviates AICI3-induced stress in a dose-dependant manner at an optimal concentration of 0.3 mmol/L. We verified that the role of NaHS in alleviating Al3＋ stress could be attributed to H2S/HS- by showing that the level of endogenous H2S increased following NaHS treatment. Furthermore, other sodium salts containing sulfur were ineffective in alleviating Al3＋ stress. NaHS pretreatment significantly increased the activities of amylases and esterases and sustained much lower levels of MDA and H2O2 in germinating seeds under Al3＋ stress. Moreover, NaHS pretreatment increased the activities of guaiacol peroxidase, ascorbate peroxidase, superoxide dismutase and catalase and decreased that of lipoxygenase. NaHS pretreatment also decreased the uptake of Al3＋ in AICI3-treated seed. Taken together these results suggest that H2S could increase antioxidant capability in wheat seeds leading to the alleviation of Al3＋ stress.
Hua ZhangZhu-Qin TanLan-Ying HuSong-Hua WangJian-Ping LuoRussell L. Jones
In this report, we demonstrate that sodium hydrosulfide （NariS）, a hydrogen sulfide （H2S） donor, promoted adventitious root formation mediated by auxin and nitric oxide （NO）. Application of the HzS donor to seedling cuttings of sweet potato （Ipomoea batatas L.） promoted the number and length of adventitious roots in a dose-dependent manner. It was also verified that H2S or HS- rather than other sulfur-containing components derived from NariS could be attributed to the stimulation of adventitious root formation. A rapid increase in endogenous H2S, indole acetic acid （IAA） and NO were sequentially observed in shoot tips of sweet potato seedlings treated with HallS. Further investigation showed that H2S-mediated root formation was alleviated by N-1-naphthylphthalamic acid （NPA）, an IAA transport inhibitor, and 2-（4-carboxyphenyl）. 4,4,5,5-tetramethylimidazoline-1-oxyl-3-0xide （cPTIO）, an NO scavenger. Similar phenomena in H2S donor-dependent root organogenesis were observed in both excised willow （Salix matsudana var. tortuosa Vilm） shoots and soybean （Glycine max L.） seedlings. These results indicated that the process of H2S-induced adventitious root formation was likely mediated by IAA and NO, and that H2S acts upstream of IAA and NO signal transduction pathways.
With the enhancement of copper （Cu） stress, the germination percentage of wheat seeds decreased gradually. Pretreatment with sodium hydrosulfide （NariS）, hydrogen sulfide （H2S） donor alleviated the inhibitory effect of Cu stress in a dose- dependent manner; whereas little visible symptom was observed in germinating seeds and radicle tips cultured in NariS solutions. It was verified that H2S or HS- rather than other sulfur-containing components derived from NariS attribute to the potential role in promoting seed germination against Cu stress. Further studies showed that NariS could promote amylase and esterase activities, reduce Cu-induced disturbance of plasma membrane integrity in the radicle tips, and sustain lower levels of malondialdehyde and H202 in germinating seeds. Furthermore, NariS pretreatment increased activities of superoxide dismutase and catalase and decreased that of lipoxygenase, but showed no significant effect on ascorbate peroxidase. Alternatively, NariS prevented uptake of Cu and promoted the accumulation of free amino acids in seeds exposed to Cu. In addition, a rapid accumulation of endogenous H2S in seeds was observed at the early stage of germination, and higher level of H2S in NaHS-pretreated seeds. These data indicated that H2S was involved in the mechanism of germinating seeds＇ responses to Cu stress.
Hua ZhangLan-Ying HuKang-Di HuYun-Dong HeSong-Hua WangJian-Ping Luo
