镉胁迫对紫花苜蓿生长及结瘤的影响

Effect of Cadmium Stress on Growth and Nodulation in Alfalfa

采用盆栽实验,以多叶苜蓿和准格尔苜蓿2个品种为材料,研究镉胁迫(0、5、10、20、50 mg/kg Cd)对紫花苜蓿生长、叶绿素含量和根瘤菌生长的影响。结果显示,镉处理浓度为5 mg/kg时,2个品种的株高、主根长、干重、叶绿素含量、根瘤数和根瘤重较之对照组均有所提高,但差异不显著。随着处理浓度增加,上述指标呈显著降低趋势,尤其是当处理浓度达到50 mg/kg Cd时,其下降幅度则是多叶苜蓿明显小于准格尔苜蓿。在重度镉胁迫下,2个品种地上部和根系的镉含量都增大,但准格尔苜蓿的镉含量高于多叶苜蓿。可见,镉浓度较低时(5 mg/kg)对苜蓿生长的影响不大,甚至有促进作用;随着镉浓度的增加,其毒害作用也随之增强,因此在镉浓度超过10 mg/kg的土壤中不宜种植紫花苜蓿。而2个品种相比较,多叶苜蓿比准格尔苜蓿具有更强的耐镉性。

Experiments were carried out to examine cadmium stress effects on growth, chlorophyll contents and nodules by comparing the responses of two alfalfa （Medicago satival L. ） cultivars （ Cd - resistance Duoye and Cd - sensitive Zhungeer） to the stress. The results indicated that Cd treatment at the 5 mg/kg level slightly improved plant height, main root length, biomass, chlorophyll content, number and fresh weight of root nodules in the two cuhivars compared with the control. With the increase of Cd concentration, the index mentioned above significantly decreased, especially at a concentration of 50 mg/kg. Toxic effect on gowth characteristics and nocules was higher in Zhungeer than in Duoye during the whole pot culture. Cd treatmet increased Cd conetent both in plant top and in root of the two alfalfa cuhivars, and the Cd content of Zhungeer is higher than that of Duoye. The results indicated that Cd stress at the low Cd level of 5 mg/kg had little effect on alfalfa growth , whereas Cd stress at the high Cd level of 10 mg/kg had significant toxic effect on alfalfa. So polluted soil with Cd concentration above 10 mg/kg was unsuitable for cultivation of alfalfa plants.