Studies On Mechanish In Cadmium Accumulation Among Different Tobacco Cultivars And Remediation Potential For Cadmium Contaminated Soil Of High Cadmium-Accumulating Rice Cultivars

Cadmium is one of the most deleterious heavy metals.Plant's root can uptake cadmium from soil,and transport to the shoot.Exposure to cadmium through the food chain leads to accumulation of cadmium in the body of human that can cause damage to human health..Since 2010,the problem of heavy metals in cigarette gradually became the focus of socialconcern..In the first part of this study,based on 10 tobacco cultivars:Komotini Basma,Liuyejian,Xiaosimao,Jinying,CY9403,Coker,Tailifu,PRH01,YZ9424,Honghuajinyuan,Kaiyang,which have stable cadmium enrichment capability,we analysed the differences of the Cd,Mn,Cu,Zn accumulation in the roots and shoots of different tobacco cultivars and screened out the high cadmium-accumulating tabacco cultivar Komotini Basma and low cadmium-accumulating tabacco cultivar Jinying under cadmium stress through hydroponic experiments.The short term cadmium uptake experiment showed that there are significant differences of root's cadmium uptake rates between the high and low cadmium-accumulating tabacco cultivars.The further study also showed that there were significant differences of ROS(Reactive oxygen species)metabolizsm between the high and low cadmium-accumulating tabacco cultivars.In the second part of this study,through field experiment,We discussed the bioremediation protential of high cadmium-accumulating rice cultivars for cadmium contaminated soil.The main results were summarized as follows:There is a close relationship between cadmium content and tobacco cultivars after the treatment.Under the same condition of cadmium treatment,there were significant differences of root and shoot cadmium concentration among tobacco cultivars.In both hydroponic and pot experiments,Komotini Basma showed the highest ability ofaccumulating cadmium,and Jinying showed the lowest ability of accumulating cadmium among the ten tobacco cultivars.In hydroponic experiment with 0.1 ?M cadmium,the cadmium concentration in the roots and shoots of Komotini Basmawas 23.94 mg kg-1 and 13.70 mg kg-1,respectively;The cadmium concentrationin the roots and shoots of Jinying was 10.94 mg kg-1 and 6.35 mg kg-1,respectively.There were also significant difference of Manganese and Zinc concentrations between these two cultivars;Through hydroponic and plot experiments,we further proved the stability of cadmium-accumulation difference of these two tobacco cultivars under different environment.A short-term(20 min)Cd uptakeexperiment proved that the root Cd uptake activity of Komotini Basma was observably higher than that of Jinying.These results suggested that the difference of root cadmium uptake activity is the major cause of cadmium-accumulation difference between the high and low-cadmium accumulating cultivars.Through measuring the contents of hydrogen peroxide(H2O2),malondialdehyde(MDA),non-protein thiol(NPT)and the activity of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)in the plant tissue,we analyzed the difference of reactive oxygen species metabolism between the high and low cadmium accumulating tobacco cultivars.The results showed that the contents of H2O2,MDA,NPT in both root and shoot of the high cadmium-accumulating tabacco cultivars Komotini Basma were significantly higher than that of Jinying.Meanwhile,the enzyme activities of POD and CAT in the shoot of Komotini Basma were higher than that of Jinying,whereas the enzyme activitie of SOD in the shoot of Komotini Basma was lower than that of Jinying.It suggested that high cadmium-accumulating tabacco cultivar showedhigher levels of reactive oxygen species and the increased NPT contents can enhance plant's tolerance to cadmium.In a field experiments,we found eight rice cultivars have strong ability to accumulate cadmium.H35 had the lowest cadmium concentration in brown rice(0.42 mg kg-1)among the 8 rice cultivars.Cultivar W4 hadthe highest cadmium concentration in brown rice(6.04 mg kg-1)among the 8 rice cultivars.Biomass is considered as an important factor for phytoremediation.H35 had the largest total biomass,which was 4251 g m-2.The total biomass of AnjanaDhan,W4 and H483 were 4007 g m-2,3329 g m-2 and 3632 g m-2 respectively.Taken together with the total biomass and cadmium concentration,we found that the cadmium accumulation in AnjanaDhan,W4 and H483 were significantly higher than that in the other five rice cultivars.Through measuring the soil cadmium content in every field plot before and after planting the rice cultivars,we found that the soil cadmium content in field plot planting H483 and Changxianggu decreased by 18%and 25%respectively,the soil cadmium content in field plot planting AnjanaDhan and W4 decreased slightly.In conclusion,it could be concluded that the AnjanaDhan,W4 and H483 have the potential to used for bioremediation of cadmium contaminated soil.