Alleviation Of Mercury-Induced Oxidative Damage In The Seedling Roots Of Medicago Sativa By Hydrogen-Rich Water

Hydrogen gas(H2)is a novel bioregulator involved in some physiological events in plants.However,whether H2 regulates plant adaptation to mercury(Hg)toxicity is not clear.In this study,pretreatment with hydrogen-rich water(HRW)is used to characterize physiological roles and molecular mechanisms of Hydrogen gas(H2)in alleviation of mercury(Hg)toxicity in.The results in this paper indicate that:1.Excess Hg caused severe oxidative damage in Medicago sativa.The results suggest that treatment with different concentration of HgCl2(1,10,100 and 500 ?M)caused dose-dependent increases in TBARS contents.Among these treatments,10 ?M HgCl2 increased the TBARS content by 91.6%compared to the chemical-free control samples.Thus,this concentration of HgCl2 was used for estimation of the role of HRW in the modulation of Hg toxicity in alfalfa plants.Further experiments showed that,pretreatment with different concentration of HRW(1,10,50 and 100%)decreased TBARS contents in Hg-stressed plants,and HRW at 10%saturation exhibited the greatest effect.These results clearly indicated that 10%saturation of HRW was able to improve Hg toxicity in alfalfa seedlings,and this concentration of HRW was used thereafter.2.Pretreatment with 10%HRW could alleviation symptoms caused by mercury toxicity,including improve seedling growth,fresh weight and dry weight.Further experiments showed that,administration of 10%HRW obviously decreased relative root ion leakage and Hg accumulation in Hg-exposed plants.The results of histochemical staining suggested that ROS was produced considerably when treated with Hg,compared with control samples;pretreatment with 10%HRW exhibited the protection against Hg-triggered oxidative damage in the root tissues of alfalfa plants.3.Hg-induced increases in total and isozymatic activities of superoxide dismutase(SOD)were significantly reversed by HRW.Further results suggested that HRW-induced the activities of guaiacol peroxidase(POD)and ascorbate peroxidase(APX),two hydrogen peroxide-scavenging enzymes,was at transcriptional levels.Meanwhile,obvious increases of the ratios of reduced/oxidized glutathione(GSH),homoglutathione(hGSH),and ascorbic acid(AsA)and corresponding gene expression were consistent with the decreased oxidative damage in seedling roots.In summary,the results of this investigation indicated that HRW was able to alleviate Hg toxicity in alfalfa seedlings by(i)alleviating growth stunt and reducing Hg accumulation,and(ii)avoidance of oxidative stress and reestablishment of redox homeostasis.