不同重金属胁迫对盐生草种子萌发特性的影响

以盐生植物盐生草为材料,研究不同重金属胁迫下其种子萌发特性,探讨盐生草种子萌发期对不同重金属的耐受程度,旨在为盐生草对重金属污染土壤修复提供理论依据。以5种主要土壤重金属污染物(Cu、Zn、Ni、Cd、Pb)胁迫处理盐生草种子,对其发芽率、发芽势、株高、鲜重、干重、根系活力和离子含量进行测定,并对以上指标进行聚类分析和主成分分析。结果表明:在5种不同重金属胁迫下,低浓度处理对盐生草种子萌发影响较小,高浓度则产生抑制作用;但是其对幼苗生长指标的影响不同,其中,株高、鲜重和根系活力在低浓度Zn^2+、Pb^2+处理下与对照差异不显著,但在5.00 mmol·L^-1 Zn^2+和3.00 mmol·L^-1 Pb^2+胁迫下显著降低,以上指标均低于各重金属胁迫下对照的55%和52%;低浓度Cu^2+、Ni^2+、Cd^2+显著抑制盐生草幼苗的株高、鲜重和根系活力,且分别在3.00 mmol·L-1 Cu^2+和Ni^2+、0.20 mmol·L^-1 Cd^2+胁迫下降低最为显著,株高、鲜重和根系活力均低于各金属胁迫下对照的40%、46%和53%;组织内各金属离子含量随处理浓度的升高而增大,同时在5.00 mmol·L-1 Zn2+,3.00 mmol·L^-1 Pb^2+、Cu^2+、Ni^2+和0.20 mmol·L^-1 Cd2+胁迫下升高幅度最大。聚类分析结果显示,以3.00 mmol·L^-1 Zn^2+,1.00 mmol·L^-1 Pb^2+、Cu^2+、Ni^2+和0.10 mmol·L^-1 Cd^2+为结点,将各金属胁迫浓度聚为两类,并对上述结点下各指标进行主成分分析,发现在重金属Zn^2+、Pb^2+、Ni^2+胁迫下,发芽指标贡献率最大,Cu^2+、Cd^2+胁迫下,生物量指标贡献率最大。上述结果说明,在重金属Zn2+浓度低于3.00 mmol·L^-1,Cu^2+、Ni^2+和Pb2+浓度低于1.00 mmol·L^-1,Cd^2+浓度低于0.10 mmol·L^-1的处理环境下,其对盐生草种子萌发和幼苗生长的影响较小;发芽指标可首选为评价盐生草萌发期耐重金属Zn^2+、Pb^2+和Ni2+的重要参数,生物量可首选为评价盐生草萌发期耐重金属Cu2+和Cd2+的重要参数。

Effects of different heavy metals on the seed germination and establishment of Halogeton glomeratus

In order to better understand the tolerance of halophyte Halogeton glomeratus to different heavy metals, this research focused on its seed germination and seedling growth when exposed to different heavy metal stresses. Indicators of seed germination and seedling growth, including the germination percentage, germination energy, plant height, fresh weight, dry weight, root activity and ion content of H. glomeratus seeds treated with five major soil heavy metal pollutants (Cu, Zn, Ni, Cd, Pb), were measured and data analysed by cluster and principal component analyses. It was found that lower concentrations of the five different heavy metals had little effect on seed germination, while higher concentrations had an inhibitory effect. However, the effects on seedling growth index were different. The plant height, fresh weight and root activity showed no significant difference under the lower concentrations of Zn²⁺ and Pb²⁺, but showed a significant decrease under the lower concentrations of Cu²⁺, Ni²⁺ and Cd²⁺.Especially, the decrease was most obvious at 5.00 mmol·L^-1 Zn²⁺, 3.00 mmol·L^-1 Pb²⁺, Cu²⁺, Ni²⁺ and 0.20 mmol·L^-1 Cd²⁺, and which is the lowest concentration of inhibition effect. The plant height, fresh weight, dry weight, root activity and ion content were lower than the control under the concentration of 5.00 mmol·L^-1 Zn²⁺, all of them showing a decrease to 55%, and which showed a decrease to 52%, 40%, 46% and 53% of the control for 3.00 mmol·L^-1 Pb²⁺, Cu²⁺, Ni²⁺ and 0.20 mmol·L^-1 Cd²⁺, respectively. Furthermore, the ion contents of the plant tissue increased with increase in heavy metal concentrations, and these increases first became obvious at 5.00 mmol·L^-1 Zn²⁺, 3.00 mmol·L^-1 Pb²⁺, Cu²⁺, Ni²⁺ and 0.20 mmol·L^-1 Cd²⁺. On cluster analysis, the metal stress concentrations were clustered into two categories based on 3.00 mmol·L^-1 Zn²⁺, 1.00 mmol·L^-1 Pb²⁺, Cu²⁺, Ni²⁺ and 0.10 mmol·L^-1 Cd²⁺, respectively. In addition, the principal component analysis showed that germination indices are mainly affected by Zn²⁺(PCA 1), Pb²⁺ (PCA 1) and Ni²⁺(PCA 1+PCA 2) treatments, and biomass has most affected by the Cu²⁺(PCA 1+PCA 2) and Cd²⁺(PCA 1+PCA 2)treatments.These results indicated that there was little effect on seed germination and seedling growth of H. glomeratus while the heavy metal concentrations were lower than 3.00 mmol·L^-1 Zn²⁺, 1.00 mmol·L^-1 Pb²⁺, Cu²⁺, Ni²⁺ and 0.10 mmol·L^-1 Cd²⁺. The germination indexes can be used for evaluating the tolerance of H. glomeratus to Zn²⁺, Pb²⁺ and Ni²⁺ during the germination period, and biomass can be used to evaluate the tolerance of H. glomeratus to Cu²⁺ and Cd²⁺.