| Cadmium(Cd)contamination in soil can not only inhibit crop growth,reduce crop yield and quality,but also do harm to human via food chain.Strigolactones can mediate the symbiosis or parasitic interaction between host plants and their roots.SL is a new plant hormone that is ubiquitous in plants.It inhibits plant branching growth and regulates plant branching with auxin and cytokinin.Meanwhile,it plays an important role in plant defense against stress condition.However,the role of strigolactone in alleviating heavy metal stress in plants is poorly understood.In this study we investigated the effects of exogenous GR24(germination releaser 24,a synthetic analog of strigolactones)on barley growth,Cd uptake and transport,photosynthesis,nutrient metabolism and active oxygen metabolism in barley under Cd stress.The aim of this study was to explore the mitigation of Cd toxicity by exogenous unipod golden lactone.The main results are as follows:1.Two barley genotypes Zhenong8(Cd-tolerant)and w6nk2(Cd-sensitive)were used for hydroponic experiments with four treatments:Control(BNS,basic nutrition solution),GR(BNS+ 1 ?M GR24),Cd(BNS+10 ?M Cd)and Cd+GR24(BNS+10?M Cd+l ?M GR24).The results showed that 10 ?M Cd treatment significantly inhibited the growth of barley seedlings,which showed yellow leaves and brown roots.Shoot height,root length and biomass were significantly reduced.Photosynthesis,chlorophyll content and net photosynthetic rate was inhibated significantly as well.The application of exogenous GR24 significantly alleviated Cd-induced inhibition in plant growth.Plant height,root length,dry weights of shoots/roots and net photosynthetic rate increased by 11.75%,47.58%,20.69%/18.18%and 68.90%in Zhenong8,compared with Cd alone treatment,and increased by 30.70%,28.89%,55.56%/50.00%,and 135.70%in w6nk2,respectively.2.The effects of exogenous GR24 on transport and accumulation of Cd and other mineral elements under Cd were investigated.The results showed that Cd content of Cd-tolerant genotype Zhenong 8 was higher than that of the Cd-sensitive genotype w6nk2.The application of exogenous GR24 significantly suppressed Cd concentration of barley seedlings.Compared with Cd-alone treatment,Cd concentration in shoots/roots of Zhenong 8 and w6nk2 decreased by 28.81%/28.20%and 26.01%/26.95%,respectively.In addition,Cd stress reduced the concentrations of Zn,Fe and Cu in shoots and roots,and application of GR24 significantly increased the three elements concentrations in barley seedlings.3.The effects of exogenous GR24 on no-enzymatic antioxidants in barley seedlings exposed to Cd stress were studied.The results showed that Cd stress induced the accumulation of H2O2 and MDA in barley shoots,but decreased NO content in shoots and roots and AsA and GSH in shoots.However,the content of AsA and GSH in roots,and DHA and GSSG in shoots and roots increased significantly compared with the control.At the same time,the ratios of AsA/DHA and GSH/GSSG decreased significantly.Under Cd+GR24 treatment,the contents of AsA and GSH increased,the contents of DHA and GSSG decreased,and the ratios of AsA/DHA and GSH/GSSG increased relative to the Cd alone treatment.4.The effects of exogenous GR24 on enzymatic antioxidase in barley seedlings under Cd stress were investigated.The results showed that Cd stress decreased the activities of NOS,SOD,POD,GPX and APX.The application of GR24 dramatically increased the activities of NOS,CAT,POD,SOD,GR,GPX,APX,DHAR and MDHAR in roots and shoots of barley seedlings.Compared with Cd treatment alone,the activities of NOS,DHAR,MDHAR and APX in shoot/root of w6nk2 barley seedlings increased by 59.13%/115.27%,30.42%/29.18%,43.44%/26.50%and 49.16%/302.82%,respectively;While the activities of POD.APX in shoot/root of Zhenong8 barley seedlings increased by 23.96%/10.67%,165.61%/26.66%,respectively.The addition of GR24 had a significant alleviation effect on oxidative damage of barley under Cd stress. |
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