镉胁迫对两种狼尾草不同生育时期生长性能、光合作用特征及镉吸收转运差异的影响

摘要

采用盆栽法研究在不同浓度(0、5、25、50、75、100 mg·kg-1)镉胁迫下美洲狼尾草(ML,Pennisetum americanum)和杂交狼尾草(ZL,P.americanum×P.purpureum)不同生育期的生长指标、光合作用特征,并比较两者耐镉性和对镉吸收转运差异.结果表明,1)相同生育期下,随Cd浓度的增加两种狼尾草株高先升高后降低,叶宽没有显著性变化,鲜重和干重逐渐降低;2)同一生育期,ML的叶绿素a和叶绿素b含量均高于ZL;低Cd浓度(5 mg·kg-1),对植株的光合指标影响不大,但Cd浓度增加后,各处理与对照相比显著下降(P<0.05),高浓度Cd处理对ZL光合作用影响要大于ML;3)ML生长性能受Cd胁迫影响比ZL要小,但ZL富集系数高于ML,ML耐镉性更好,而ZL修复镉污染土壤的能力更强;4)根系是主要富集部位并且镉从根系往地上部位转移系数较低,3个生育期中幼苗期植株中Cd含量最高.%The growth,photosynthetic indices of Pennisetum americanum(ML) and P.americanum×P.purpureum(ZL) under different cadmium(0,5,25,50,75,100 mg·kg-1)were investigated by pot experiment and make a comparison between the two cadmium tolerance and the difference on the absorption and transport of cadmium.Results showed that: 1) the plant height decreased after increasing Cd concentration,fresh weight and dry weight decreased while leaf width changed no significant with the Cd concentration increased at the same growth stage;the indicators above increased gradually with the extension of the growth period at the same Cd concentration,however leaf width and fresh weight of ZL showed bigger;2) At the same growth stage,Chla and Chlb content in ML were more than ZL.When Cd concentration at 5 mg·kg-1,it showed little effects on the net photosynthetic rate,transpiration rate,intercellular carbon dioxide concentration,but with the Cd concentration increased each treatment became significantly decreased compared with the control(P<0.05),which indicated that high concentrations of Cd treatment had significant effect on the photosynthesis of Pennisetum especially ZL.3) Growth performance of American pennisetum was better than hybrid pennisetum,while the bioconcentration factor was less,indicating that the former had better tolerance to Cd,and the latter was more suitable for the remediation of cadmium contaminated soil.4) the root system is the main bioconcentration site and Cd in root part transfered little to the overground part,in three growth stages,the content of Cd was the highest in seedling stage,which showed the seedling stage was when the plant was the most susceptible to Cd stress.ZL had a better effect than ML on the remediation of cadmium contaminated soil.If the soil under low Cd concentrations(<1.0 mg·kg-1),pennisetum still can be used as edible forage.