Effects Of Nitrogen-doped Carbon Nanoparticles On Accumulation Of Cadmium And Expression Of Cadmium Transporter Gene In Brassica Napus

Cadmium(Cd)is one of the most harmful heavy metal species.Up to date,the Cd pollution of soils is becoming more and more severe.Therefore,it is urgent that green remediation strategies be developed.Phytoextraction of hyperaccumulators,which can be used for the removal of heavy metals from contaminated soils,is an important remediation method of heavy metal-polluted soils.The efficiency of phytoremediation is dependent on the biomass and the accumulation ability of hyperaccumulators.Brassica napus,a Cd hyperaccumulator,has great biomass and wide adaptability showing a great application potential for soil remediation.Owing to the outstanding properties of carbon nanoparticles,such as porosity,large specific surface area,dispersibility in water,low biotoxicity,excellent biocompatibility and low manufacture cost,they contribute to a broad range of environmental and agricultural applications.However,there is little information on their application in the remediation of soils polluted with heavy metals.In this study,we investigated that the effects of 5‰ nitrogen-doped carbon nanoparticles(N-CNPs)on the growth,Cd accumulation and expression of Cd transporter genes in B.napus exposed to different levels of Cd treatments.The results showed as follows:(1)5,10 and 15 mg/kg Cd exerted obvious harmful effects on B.napus as reflected as the decrease in leaf chlorophyll content and biomass,and the increase in membrane lipid peroxidation.N-CNPs application significantly alleviated the inhibition of growth and decreased the levels of membrane lipid peroxidation in B.napus.As compared with the treatments without N-CNPs,leaf chlorophyll content was increased by 15.6%,11.0% and15.6%,respectively,when B.napus was exposed to 5,10,15 mg/kg Cd for 30 days.Malondialdehyde(MDA)content was increased by 24.4%,21.2% and 16.2% in shoots,and31.5%,18.1% and 22.2%,respectively.The biomass was increased by 18.9%,27.8% and20.9% in shoots and 18.3%,22.2% and 16.0% in roots,respectively.(2)N-CNPs application significantly enhanced the absorption of Cd in B.napus.Relative to the treatments without N-CNPs,the Cd content was increased by 17.2%,11.8%and 6.0% in shoots,and 40.5%,40.9% and 21.5% in roots,when B.napus was exposed to 5,10,15 mg/kg Cd for 30 days.(3)N-CNPs application significantly enhanced the expression levels of Cd transporter genes BnHMA3 and BnHMA4.As compared with the treatments without N-CNPs,thetranscripts of BnHMA3 were increased by 63.9%,627.8% and 76.3% in shoots,and 163.5%,208.4% and 143.9% in roots,respectively,when B.napus was exposed to 10 mg/L Cd for 3,6and 6 h.The expression of BnHMA4 was increased by 466.2% in shoots and 378.5% in roots.However,N-CNPs adding had no obvious effects on the expression of BnPCS.These findings imply that the enhancement of BnHMA3 and BnHMA4 might be closely related to the increased Cd accumulation and the Cd tolerance in B.napus.