Study On The Mechanism Of Graphene Oxide Uptake Of Cadmium In Wheat Seedlings

In this paper,the effects of cadmium(Cd)on the root morphology,photosynthesis,antioxidant enzyme system of wheat seedlings and migration and accumulation of Cd in wheat seedlings were studied by laboratory hydroponic method in the presence of graphene oxide(GO).The main results are as follows.(1)Effects of Cd on roots morphology of wheat seedling and Cd uptake in the presence of GO.Compared to Cd alone,Cd combined with GO,had a more inhibitory effect on the total root length,total root surface area,average root diameter,root hair number and tubulin of wheat seedlings when the concentration of GO ranged from 5 mg L'1 to 40 mg L-1.The inhibitory effect increased with an increase of the GO concentration(P<0.05),indicating GO expanded the toxicity of Cd.The results of transmission electron microscopy showed that GO was detected in roots and leaves under the single GO treatment or com'bined treatment of GO and Cd.Compared with the control,GO alone,GO combined with Cd induced more damage of organelles and cell membrane of wheat seedling roots and leaves.Compared with single Cd treatment,GO ehanced Cd content in roots and leaves,and Cd content increased with the increase of concentration,and there was a dose-effect relationship.In addition,the Cd content in wheat roots was greater than that of in leaves,indicatingGO promoted the absorption of Cd by wheat.(2)Effects of Cd on photosynthesis of wheat seedlings in the presence of GOCompared with single Cd treatment,the inhibition of Cd on transpiration(Tr),photosynthesis(Pn),Stomatal Conductance(gs),maximal photochemistry efficiency(Fv/Fm),actual quantum yield((?)PSII)and electron transfer rate(ETR)and chlorophyll a,b,total chlorophyll content and Ribulose-1,5-bisphosphate carboxylase/oxygenase(RuBisCO)was significantly higher than that with single Cd treatment(P<0.05)when the concentration of GO was 5 mg L-1.And with the increase of GO concentration,wheat seedlings Tr,Pn,gs;Fv/Fm,cpPSII,ETR,chlorophyll a,b,total chlorophyll content and RuBisCO concentration decreased significantly,while intercellular carbon dioxide(Ci)increased significantly.(3)Effect of Cd on biochemical indexes of wheat seedlings in the presence of GOCompared with Cd treatment alone,at the low concentration of GO(5 mg L-1),the content of cytochrome P450 in wheat leaves and roots increased significantly,which is the resistance of seedlings to stress.Compared to Cd alone,the superoxide anion(O2.-)and hydrogen peroxide(H2O2)concentrations of combined treatment in roots and leaves of the seedlings were significantly higher at the GO concentration of 5 mg L-1.Due to the large amount of O2.-and H2O2,the balance of oxidation and reduction in the body is destroyed.At the same time,superoxide dismutase(SOD)and peroxidase(POD)in the enzymatic protection system also increased significantly to remove O2.and H2O2.Compared with Cd treatment alone,the malondialdehyde(MDA)content in the combined treatment increased significantly at the GO concentration of 5 mg L'1,indicating that ROS caused membrane damage in wheat leaves and roots,eventually leading to lipid peroxidation and roots damage.The damage degree of roots is more obvious than the leaves.