Abstract: 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⁺.

Key words: soil pollution, heavy metals, Halogeton glomeratus, seed germination, principal component analysis