| With the explosure of heavy metal contamination scandals in recent years, it has attracted great attention in china society. It is no time to delay to control heavy metal pollution, especially the cadmium pollution. At this point, the research and development of the remediation technologies of cadmium contaminated soil have become the hotspot and focus in this area. Phytoremediation is a new, economic, and the environmental technology, and it has been regarded as an important solution to remediate polluted contamination in recent years. Efficiency of the phytoremediation is often limited on the tolerance of plants on against heavy metal. The growth of plants will be limited when plants suffered the excessive heave metal stress, and the efficiency of phytoremediation will be consequently negative affected.In this study, exogenous nitric oxide(SNP) was supplemented in order to investigate the effects and the function mechanisms of NO on ameliorating the Cd-inducd stress. The physiological response to Cd, absorbance and transportance of Cd, antioxidant system and S-nitrosylation system of Boehmeria nivea(L.) Gaud(ramie) have been studied to investigate the effects of exogenous NO on plant growth, identify the NO-involved reaction and the substracts of this reaction, and anylise the inner connection between S-nitrosylation and antioxidant system. The main conclusions has been present as follow:(1) Application of exogenous nitric oxi de significantly ameliorates the growth inhibition of ramie induced by Cd. Under the treatment of the SNP, the biomass, shoot length and soluable protein content has increased markedly. However, this effect exhibited a property of concentration-depedent. Low concentration of SNP induced a relatively positive effect. But this effect was not visible with the treatment of high concentration of exogenous nitric oxide. Moreover, exogenous nitric oxide promotes the capacity of absorbance of Cd in plant, and enhan ces the transpotance from roots to shoots. This effect is also correlates with the concentration of SNP.(2) Exogenous nitric oxide enhances the tolerance against oxidative stress, inhibites the over-accumulation of ROS. The activities of SOD 、 POD and the efficiency of ascorbate-gluthione cycle are also promoted. The effects of exogenous NO were conducted by releasing NO?. Besides, the ameliorating effects varied with time. Different degrees of effects were found between short term(24h) and long term(72h). This indicated that the function of NO may involve different complex mechanisms correlated with plant regulation.(3) Exogenous nitric oxide were found to correlate with cellular NO and S-nitrosylation positively. GSNOR, as an important enzyme functions in regulation of cellular S-nitrosylation, were found involved in regulate the S-nitrosylation reaction induced by exogenous NO. The substrate of the reaction(GSNO) catalyzed by GSNOR were also investigated to regulate GSNOR activity in turn. Besides, the relationship between S-nitrosylation and antioxidant system was identified. However, this connection seemed to be two-phase. Under, low S-nitrosylation level, increase in S-nitrosylation help to trigger the production of gluthione(GSH) and ameliorate the inhibition of antioxidative enzyme and enhance the efficiency of antioxidant system. However, thie effect were reversed under high S-nitrosylation level.Above all, application of exogenous nitric oxide can significantly ameliorate the inhibition of growth induced by Cd and enhance the efficiency of antioxidant system. This finding could provide a new solution to phytremediation. Moreover, this study identified the important role of S-nitrosylation in NO-induced ameliorating effects. And the relationship was investigated between S-nitrosylation and antioxidant system. Our work could render a innovative idea for the study of plant tolerance against Cd. |
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