Cr6+对人工湿地薏苡光合特性和微量元素吸收的影响

为深入了解Cr⁶⁺胁迫对人工湿地植物薏苡光合特性和微量元素吸收的影响，该文通过构筑微型垂直流薏苡(Coix lacryma-jobi)人工湿地，采用1/2 Hoagland’s营养液配制的含0、5、20、40 mg·L^-1 Cr⁶⁺废水为灌溉用水，研究铬胁迫对人工湿地植物生长、光合特性、抗氧化酶活性和微量元素吸收等的影响。结果表明：(1)低浓度(5 mg·L^-1)Cr⁶⁺对薏苡的株高、茎粗和分蘖影响不显著，高浓度(20、40 mg·L^-1)Cr⁶⁺则显著抑制薏苡的生长。(2)低浓度Cr⁶⁺处理下，薏苡叶片净光合速率(P_n)、气孔导度(G_s)和蒸腾速率(T_r)有不同程度的提高，提高幅度分别为6.8%～54.8%、13.0%～40.3%和9.1%～36.4%。高浓度Cr⁶⁺处理下，叶片P_n、G_s

Effects of Cr6+ on photosynthetic characteristics and trace element absorption of Coix lacryma-jobi in constructed wetland

In order to understand the effects of Cr⁶⁺ stress on the photosynthetic characteristics and trace element absorption of Coix lacryma-jobi, we investigated the effects of Cr stress on the growth, photosynthetic characteristics, antioxidant enzyme activity and microelement absorption of C. lacryma-jobi by constructing a miniature vertical flow C. lacryma-jobi artificial wetland with 1/2 Hoagland''s nutrient solution containing 0, 5, 20, 40 mg·L^-1 Cr⁶⁺ wastewater as irrigation water. The results were as follows:(1)Low concentration(5 mg·L^-1)of Cr⁶⁺ had no significant effects on plant height, stem thickness and tillering of C. lacryma-jobi, while high concentrations(20, 40 mg·L^-1)of Cr⁶⁺ significantly inhibited the growth of C. lacryma-jobi.(2)Net photosynthetic rate (P_n), stomatal conductance(G_s)and transpiration rate(T_r)of C. lacryma-jobi leaves were increased to different degrees under low Cr⁶⁺ treatment, with the increases ranging from 6.8% to 54.8%, from 13.0% to 40.3% and from 9.1% to 36.4%, respectively. Under the high concentration of Cr⁶⁺ treatment, the P_n, G_s and T_r of leaves decreased significantly, but the intercellular CO₂ concentration(C_i)increased significantly.(3)Both superoxide dismutase(SOD)and peroxidase(POD)activities of C. lacryma-jobi leaves increased with increasing treatment time; SOD activity of C. lacryma-jobi leaves did not significantly differ from the control under low Cr⁶⁺ treatment, and was significantly inhibited under high Cr⁶⁺ treatment. The POD activity and malondialdehyde(MDA)content of C. lacryma-jobi leaves increased with the increase of Cr⁶⁺ treatment concentration.(4)The absorption of Cu, Fe, Mn and Zn by roots, stems and leaves was significantly inhibited by high concentration of Cr⁶⁺ treatment.(5)The removal rate of Cr⁶⁺ by the artificial wetland was up to 99% under 5 and 20 mg·L^-1 Cr⁶⁺ treatments, and 86% under 40 mg·L^-1 Cr⁶⁺ treatment. All the results indicate that Cr⁶⁺ stress leads to a significant decrease in the absorption of Fe, Mn, Zn and Cu, hinders photosynthesis, impairs antioxidant systems and inhibits plant growth, which ultimately leads to a decrease in the ability of the artificial wetland to treat Cr⁶⁺ containing wastewater.