| Part of farmland is polluted by heavy metal in our country.Screening low crop varieties can reduce the human health risk of eating the agricultural products which is planted on the land of which the cadmium(Cd)pollution degree is mild or light,thus the work is of great significance.Zea Mays are China’s second largest food crops,but it’s rarely to screen varieties of low cadmium accumulation in northeast of China.This experiment selected 18 mazie cultivars which are planted in northeast of china to plant under cadmium stress conditions(5 mg·kg-1),then the pot expriment aimed to find out the rule of accumulation and translocation of cadmium,and to screen out the cutivars the accumulation of which are lower and more,and to explore the relationship between Cd states in soil and Cd content in different parts of maize.The essay draws several conclusions as follows:1 The biomass and yield of the control group and experimental group had significant differences.The biomass of experimental group and control group’s range in different maize varieties were respectively 0.39～0.39 kg/basin,0.40～0.56 kg/basin,the average of them were 0.47 kg/basin,0.48 kg/basin,respectively.The yeild of experimental group and control group’s range in different maize varieties were respectively 0.16～0.16 kg basin,0.16～0.27 kg/basin,and the average of them were respectively 0.21 kg/basin,0.21 kg/basin.The mean biomass of experimental group compared with control group fall 0.01 kg/basin,While the mean yield almost remained unchanged.2 The content of Cd in root,stem,leaf,seed in the control group and experimental group all have significant differences,and most of maize varieties’ Cd accumulation were in the rule of root>leaf>stem>grain.The Cd content of root in the experimental group and control group were respectively 4.80～8.76,0.054～0.150 mg·kg-1,the average of them were respectively 7.36,0.087 mg·kg-1.The Cd content of leaf in experimental group and control group were respectively 0.30～4.15,0.029～0.3062 mg·kg-1,the average of them were respectively 1.87,0.046,5 mg·kg-1.The Cd content of stem in the experimental group and control group were respectively 0.42～1.98.,0.01～0.05 mg·kg-1,the average of them were respectively 1.11,0.029 mg·kg-1.The Cd content of grain in the experimental group and control group were respectively 0.016～0.363,0.001,7～0.003 7 mg·kg-1,the average of them were respectively 0.144,0.002,7 mg·kg-1.The Cd content in stem,leaf of all the cultivars in control group and the 3,15 cultivars in experimental group didn’t exceed the national feed hygiene standards(<0.5mg·kg-1),The Cd content in grain of all the cultivars in control group and the 1,3,4,9,12,13,14,15,18 cultivars in experimental group didn’t exceed the national food hygiene standards(<0.1 mg·kg-1).According to the evaluation of maize biomass,grain and leaf and stem’s cadmium content,enrichment coefficient,transferring coefficient,4 of maize cultivars named Xin Dongdan16,Dongdan60,Shen He118 and Fu You 9 can be fistly recommended to cultivate on the land of which the Cd pollution degree is mild and moderate for planting.3 The bioconcentration and translocation factors of the cultivars in experimental group and control group had significant difference(P<0.05)in experimental group,the root’s bioconcentration factor of different cultivars were>1,the stem’s bioconcentration factor of different cultivars were<0.5,the leaf’s bioconcentration factor of different cultivars were≤0.9,the grain’s bioconcentration factor of different cultivars were<0.1.The ability about accumulating Cd of leaf were slightly stronger than stem,but it’s still below the root’s,while the grain’s ability of accumulating cadmium were the lowest.4 The form of Cd in experimental group were mainly exchangeable state and residual state,the exchangeable state of Cd had a significant positive correlation with content of Cd in stem,the content of Cd in leaf,the content of Cd in total above ground in cultivars,and the translocation coefficient of stem and leaf.The carbonate bound state,Fe Mn oxide bound fraction and organic matter bound didn’t have any significant corresponding with the content or bioconcentration or translocation factor of any part of the plant.The residual form of Cd had significant negative correlation with the content of Cd in leaf,grain,as well as the above ground total Cd content.5 The hydroponic experiments selected No.18,No.3 as low Cd accumulation maize cultivars and No.6,No.8 as Cd sensitive maize varieties from the pot experiment.Through the pattern of hydroponic cultivars,the POD,SOD,CAT,soluble protein content of four maize varieties in root,stem and leaf was firstly increased and then decreased with the increasing of cadmium concentration,while the MDA content always increased with the increasing trend of cadmium.When the Cd concentrations is no more than 8 mg·L-1,some outside adversity that the increasing of Cd concentrations made the activity of antioxidant enzyme increasing as well for reaction;while the Cd concentrations rose further,the activity of antioxidant enzymes would be inhibited.Under Cd stress,the contents of POD,SOD,CAT and soluble protein in low accumulation cultivars were higher,and the content of MDA was lower than that Cd sensitive maize cultivals.The results showed that the low accumulation cultivars had the higher antioxidant enzyme activities,and alleviated peroxidation of membrane lipid,which could reduce the damage of Cd to the normal physiological activities of the cells. |
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