| Sulfur dioxide (SO2) has been considered as an atmospheric pollutant which has serious toxicity to animals. Recently, more and more researches showed that SO2plays a wide range of biological roles in animals including regulating cardiac function, vasodilator effect in vascular tissues and having a anti-atherogenic effect. Whether SO2plays a role as signaling molecule in plants is not clear. In this paper, we used NaHSO3/Na2SO3(1:3, M/M) as SO2donor to investigate the anti-oxidation mechanism of SO2in the germinating process of the wheat seeds that exposed to aluminum (Al3+) or drought stress. Al3+stress has a strongly inhibited effect on the wheat seeds germination, and the inhibitory effect gradually increased with Al3+concentration rose. At15mmol/L AICl3, the germination of the wheat seeds is reduced by about50%compared to the control group. We defined15mmol/L is the half inhibitory concentration. In this paper, we found that the germination rates of wheat seeds, the contents of reducing sugar and soluble protein, the activity of amylase and esterase increased obviously in the wheat seeds that pretreated with SO2donor. These showed that SO2donor pretreatment had a beneficial effect to the mobilization of wheat seeds storage substances and the expression of hydrolase activity then promoted the germination of wheat seeds. Reactive oxygen species burst and the oxidative damage induced by which is one of the most important mechanism of Al3+stress. We found that pretreated with SO2donor could significantly reduce the contents of superoxide anion (·O2-); hydrogen peroxide (H2O2) and malondialdehyde (MDA). Which indicated that SO2alleviated the oxidative damage that caused by Al3+stress. Further studies showed that, pretreated with SO2could increase the activities of peroxidase (POD), ascorbate peroxidase (APX) and peroxide catalase (CAT), but the activity of lipoxygenase (LOX) was reduced. These results showed that SO2played as a antioxidant signal in wheat seeds response to Al3+stress.Similar to Al3+stress, drought stress also cause reactive oxygen species burst in plants. We verified the experimental results with drought stress to test whether SO2has the a similar effect in wheat seeds exposed to drought stress. The germination rates of wheat seeds which pretreated with SO2donor were significantly improved, the reducing sugar and soluble protein contents were increased, and the activities of amylase and esterase had also been enhanced. The contents of O2, H2O2, and MDA was significantly reduced, the activities of POD, APX and CAT were increased and the activities of LOX was reduced. All of these showed that the SO2donor had the same effects on the wheat seeds that exposed to drought stress, and also conducive to the germination of wheat seeds.H2S is a new signaling molecule with antioxidant function in plants. The content of endogenous hydrogen increased in the seeds that pretreated with SO2donor. The increasing content of H2S in the wheat seeds that pretreated with SO2donor suggested SO2promote wheat seeds germination in the signal transduction pathway mediated by endogenous H2S. Aleurone cells is an important and indispensable organization to seed vigor and seed germination. During the germination of the seed, the gibberellic acid (GA) synthesized by embryonic secreted to endosperm storage organ, and promoted endosperm develop into whole plants. We used the wheat seed aleurone as experimental material to study the effect of H2S that plays in the program cell death of aleurone. The results showed that H2S could significantly improve the activity of amylase and esterase in the aleurone layer, significantly delayed the programmed cell death of aleurone layer, and mitigated the programmed cell death which caused by GA. These results indicated the increasing content of H2S that caused by SO2donor pretreated had a inhibition effect on the programmed cell death of wheat aleurone layer. thus contributed to the germination of wheat seed. |
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