基于相关分析和主成分分析的紫花苜蓿抗镉胁迫研究

Cadmium stress resistance of Medicago sativa L. based on correlation analysis and principal component analysis

  • 摘要: 【目的】探究紫花苜蓿种子在镉(Cd)胁迫下幼苗生理生化指标的变化,筛选出典型指标因子,为植物修复土壤中的Cd污染提供理论依据。【方法】紫花苜蓿种子经不同Cd浓度(0、1、5、10、15、30和50 mg/L)胁迫处理后培养生长,对其幼苗生理指标进行测定;并采用相关分析和主成分分析法对各个指标进行分析,评价Cd胁迫对紫花苜蓿生理状况的影响。【结果】随Cd浓度的增加,紫花苜蓿根细胞活力及子叶的叶绿素和可溶性蛋白含量逐渐减少,子叶的丙二醛(MDA)、羟自由基(·OH)和超氧阴离子自由基(O2-·)含量逐渐增加,幼苗中Cd含量及子叶的脯氨酸含量、可溶性糖含量、过氧化氢(H2O2)含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性和过氧化氢酶(CAT)活性呈先增后减的变化趋势;当Cd浓度为1 mg/L时,SOD活性达最大值320 U/(g·min);当Cd浓度为5 mg/L时,可溶性糖含量达最大值11.276µg/g;当Cd浓度为10 mg/L时,脯氨酸含量和CAT活性达最大值,分别为80.147µg/g和77 U/(g·min);H2O2含量、POD活性和Cd含量在Cd浓度为30 mg/L时达峰值,分别为15.75μmol/g、1412 U/(g·min)和2.135 mg/g。相关分析结果显示,Cd浓度与紫花苜蓿子叶中的·OH、O2-·和MDA含量及整株幼苗中Cd含量呈极显著正相关(P<0.01,下同),与叶绿素a、叶绿素b、总叶绿素、可溶性蛋白和可溶性糖含量及CAT活性和根细胞活力呈极显著负相关。主成分分析结果显示,第一主成分(PC1)和第二主成分(PC2)累积贡献率为87.50%,根细胞活力在PC1中载荷最高,可溶性糖含量在PC2中载荷最高。【结论】紫花苜蓿对外环境中的Cd有一定富集作用,可考虑将其用作修复Cd污染地区土壤的植物之一,且根细胞活力和可溶性糖含量可作为评价Cd胁迫对紫花苜蓿影响的重要指标。

     

    Abstract: 【Objective】The purpose of the study was to explore the changes of physiological and biochemical indexes of Medicago sativa L.seedlings under cadmium (Cd) stress,to screen out the typical index factors,and to provide a theo-retical basis for phytoremediation of Cd pollution in soil.【Method】M.sativa seeds were cultured after stress treatments with different Cd concentrations (0,1,5,10,15,30 and 50 mg/L),and the physiological indexes of the seedlings were determined.Correlation analysis and principal component analysis were used to analyze each index,and the effects of Cd stress on the physiological status of M.sativa were evaluated.【Result】With the increase of Cd concentration,the root cell vitality,chlorophyll and soluble protein contents of M.sativa cotyledons gradually decreased,while the contents of malondialdehyde (MDA),hydroxyl radical(·OH) and superoxide anion radical (O2-·)in cotyledons gradually increased,and the contents of Cd in seedlings,proline content,soluble sugar content,hydrogen peroxide (H2O2) content,superoxide dismutase (SOD) activity,catalase (POD) activity and catalase (CAT) activity in cotyledons showed a tendency of in-creasing and decreasing.When the concentration of Cd was 1 mg/L,the SOD activity reached the maximum value of 320U/mg.When the concentration of Cd was 5 mg/L,the soluble sugar content reached the maximum value of 11.276µg/g.When the concentration of Cd was 10 mg/L,proline content and CAT activity reached the maximum value of 80.147µg/g and 77 U/(g·min) respectively.H2O2 content,POD activity and Cd content reached the peak at a Cd concentration of 30mg/L,which were 15.75μmol/g,1412 U/(g·min) and 2.135 mg/g respectively.The results of correlation analysis showed that Cd concentration was extremely significantly positively correlated with the contents of·OH,O2-·and MDA contents in M.sativa cotyledons and Cd content in the whole seedling (P<0.01,the same below),and extremely signifi-cantly negatively correlated with the contents of chlorophyll a,chlorophyll b,total chlorophyll,soluble protein and soluble sugar,as well as with CAT activity and root cell vitality.The results of principal component analysis showed that the cumulative contribution rate of the first principal component (PC1) and the second principal component (PC2) was87.50%,the root cell vitality had the highest loading in PC1,and the soluble sugar content had the highest loading in PC2.【Conclusion】M.sativa has a certain enrichment effect on Cd in the external environment,which can be considered as one of the plants to repair Cd-polluted areas,and the root cell vitality and soluble sugar content can be used as impor-tant indexes to evaluate the effect of Cd stress on M.sativa.

     

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