| Farmland polluted by heavy metals has become a threat to agricultural sustainable development and human health.Remediating the pollutted farmland has draw many researchers'attention all over the world.A set of hydroponic culture experiments,with the treatment of Cd2+concentrations at 0.0,0.5,1.0,2.0,5.0,10.0 mg·L-1,were carried out to evaluate the effects of cadmium on the seed generation of a variety of Perilla frutescens seeds.And a set of hydroponic culture experiments with the treatment concentrations of Cd2+were 0.0,2.0,5.0 and 10.0 mg·L-1 were employed to evaluate the effects of cadmium on the seedlings.The physiological and biochemical characteristics of cadmium enrichment in Perilla frutescens under cadmium stresses were studied.The gene expressions of cytochrome P450 reductase and anthocyanin which related to detoxification in the cell were analyzed in this study.Field experiments were conducted using the higher accumulation ability germplast to remediate Cd polluted soils,and the bioremediation effect of Perilla frutescens-rice crop rotation system was evaluated.The main results are shown as follows(1)Seed germination,the length of root and shoot of Perilla frutescens in four ecological types were investigated by treating seeds with the solution containing Cd2+ at 0.0,0.5,1.0?2.0,5.0,10.0 mg·L-1.There were no significant promotion or inhibition effects on genermination rate and germination potential of Perilla frutescens(L.)Britt.Var.Acuta(Thunb.)Kudo,Perilla frutescens(L.)Britt.Var.argut)-A(Perilla-A)and Perilla frutescens(L)Britt.Significant inhibition effects were observed in Perilla frutescens(L.)Britt.Var.arguta)-B(Perilla-B)under Cd2+concentrations at 10.0 mg·L-1.The results showed that the lengths of root and shoot of the four type Perilla frutescens were inhibited under cadmium stress conditions.(2)A set of hydroponic culture experiments,with the treatment concentrations of Cd2+ at 0.0 mg·L-1,2.0 mg·L-1,5.0 mg·L-1 and 10.0 mg·L-1,were set up to detemined the biomass,plant height,root length,net photosynthetic rate of Perilla frutescens,it showed that the relative growth rate of the plant were declined with the increasing of cadmium concentration in thhese experiments.The highest biomass(0.10?0.51 g·plant-1)were observed in Perilla-A among the 4 types of plant through out at all the 4 treated Cd concentration levels.And the cadmium content in Perilla-A was from 348.1 mg·kg-1 to 1416.7mg·kg-1,the accumulated cadmium in the plant was from 141.7?g plant-1 to 454.0 ?g plant-1,showing bioconcentration coefficient between 141.7 and 265.5,with ransportion factor of Cd between 0.04 and 0.10.(3)Under designed plant density and fertilization methods,there were no significant difference in biomass were observed among different treatments..In year 2011,the average biomass(dry weight,DW)of Perilla-A was 0.79 kg/m2,the amount of cadmium accumulated in Perilla-A were from 37.77 to 72.91 ?g·plant-1.which suggested the amount of cadmium up to 1078.80 to 1110.75·g/m2.Bioconcentration coeffient of Cd were from 0.42 to 0.75,Transportion factor of Cd were between 0.49 and 1.14.Significant differences were found among different treatments.According the yield and total Cd extracted by the plant,a plan,with plant spacing 20 cm by 20 cm and recommomed fertilizer application is organic fertilizer combinded with 45%compound fertilizer,was suggested to conduct field experiments in further study.(4)After a 3 year plant remediation experiment by Perilla-rice crop rotation,soil heavy metal content significantlydeclined from 4.72 mg·kg-1 to 0.28 mg·kg-1.The activities of phosphomonoesterase and catalase were decreased,and the activities of peroxidase,polyphenol oxidase,urease and uucrase in the soils were increased.the average cadmium concentration in grains of rice significantly declined from 1.46 mg·kg-1(1st year)to 0.77 mg·kg-1(3rd year)the amout of cadmium accumulated in rice was dropped from 112.96?g to 11.13?g per plant.(5)The gene expressions of cytochrome P450 reductase and anthocyanins were analyzed by fluorogenic quantitative PCR technique.The result showed that both the genes up-regulated in leaf after 3 d treatment by Cd,while down-regulated under higher concentration of Cd(10.0mg·L-1)after a longer period treatment.Diffent resusts were found in root of the plant.After 3 d treatment,the gene expression of cytochrome P450 reductase in root were decreased while anthocyanins were increased.The revese was found after a longer period treatment at higher concentration of Cd(10.0mg·L-1)condition. |
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