Invasive Species Compendium

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Abstract

Responses of growth, photosynthesis of Ulmus pumila 'Jinye' and Shepherdia argentea to soil zinc contamination.

Abstract

Objective: To screen suitable plant species to be used in zinc-polluted area. Method: A pot experiment was conducted to evaluate the phytoremediation capability of 2-year-old Ulmus pumila 'Jinye' and Shepherdia argentea saplings to zinc contamination. By adding exogenous zinc into soil in which background value was 125 mg.kg-1, different zinc concentration treatments were set, including CK (0 mg.kg-1), T1 (300 mg.kg-1), T2 (500 mg.kg-1), T3 (1 000 mg.kg-1), for 90 days in plastic buckets. Plant height, biomass, photosynthesis and zinc content distribution in various parts of the plants were measured, and tolerance index (Ti) (%) based on dry biomass and growth parameters was used to evaluate saplings tolerance ability under zinc stress. Result: Plant height, biomass and Ti decreased with the increasing zinc concentration. The Ti of U. pumila 'Jinye' and S. argentea reached 81%, 66% and 73%, 57% under the concentration of T1 and T2, respectively, with better zinc endurance abilities. The root-shoot ratio of U. pumila 'Jinye' displayed no significant differences as compared with CK under the concentration of T1 and T2, while the ratio of U. pumila 'Jinye' was significantly lower than that of CK when the zinc concentration reached up to T3. With the increasing zinc concentration, the root-shoot ratios of S. argentea under different treatments were all declined significantly when compared with CK. The synthesis of photosynthetic pigments in the process of plant growth was inhibited by zinc stress. Meanwhile, the contents of chlorophyll a, chlorophyll b and total chlorophyll in two cultivated plants were all decreased with the increasing zinc concentration (P<0.05). The net photosynthetic rate (Pn) of both plants declined dramatically with increased Zn concentration. The stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr) of the U. pumila 'Jinye' and S. argentea had similar variation patterns with the Pn, which were all significantly lower than those of the CK. With the increase of Zn concentration in the soil, the zinc content of root and above-ground part presented increasing trends and the accumulation content of the two parts both reached the maximum in T3. The average concentration of zinc in root of U. pumila 'Jinye' and S. argentea were 25.31-345.31 mg.kg-1 DW and 29.01-159.51 mg.kg-1 DW, respectively. The average concentration of zinc in above-ground part of U. pumila 'Jinye' and S. argentea were 21.32-296.18 mg.kg-1 DW and 17.98-139.75 mg.kg-1 DW, respectively. The translocation coefficient of U. pumila 'Jinye' and S. argentea were 1.20, 1.01 and 1.11, 1.39 under T1, T2, respectively. Conclusion: U. pumila 'Jinye' and S. argentea had a high tolerance to zinc stress and the good ability to migrate zinc to the upper part under soil zinc contents of 625 mg.kg-1. Thus, U. pumila 'Jinye' was suitable for virescence in the zinc-polluted area. As an introduced exotic species, S. argentea had good endurance to soils polluted by zinc and can be used for afforestation in zinc-polluted area in western China.