德国鸢尾对Cd胁迫的生理生态响应及积累特性

通过盆栽研究了Cd胁迫下德国鸢尾的生长状况、生态效应、生理特性及吸收和富集Cd的能力.结果表明:德国鸢尾对小于5 mg/kg的Cd有较强的耐性,适用于城区土壤修复；Cd浓度大于5 mg/kg时抑制德国鸢尾生长,降低了其生态效应.随着Cd浓度的增大,德国鸢尾根系活力、叶绿素含量和含水量逐渐降低,游离脯氨酸和可溶性糖含量先升高后降低,细胞膜透性逐渐升高.Cd在德国鸢尾体内分布为根系＞地上部分,随着Cd浓度的增大,德国鸢尾根系和地上部分Cd积累浓度逐渐升高、富集系数和转运系数逐渐降低；Cd浓度为20 mg/kg时德国鸢尾对Cd的积累量最大,为2.122 mg/plant.

Physiological-ecological responses of Iris germanica L. to Cd stress and its accumulation of Cd

The valuable ornamental plant Iris germanica L., which widely distributed in city gardens and on the road-sides in our country, is a kind of groundcover plant. It is usually applied for green and courtyard ornamentation. Using Iris germanica L. to remedy urban soil polluted by cadmium (Cd) can not only purify the soil but also obtain landscape and ecological benefits. The responses of Iris germanica L. to Cd stress and its accumulation of Cd were studied under five Cd concentrations (0.5, 1, 5, 10 and 20 mg/kg) with pot culture experiments. In comparison, the same setup without Cd addition was used as a control treatment. The experiment was conducted with a completely randomized design. Some morphological indexes (plant height, leaf area, tiller number, shoot biomass and root biomass), ecological indexes(net photosynthesis rate and transpiration rate) and physiological indexes (chlorophyll content, root activity, water content, contents of free proline and soluble sugar) were observed in green stage and flowering stage of Iris germanica L..The distribution of Cd in Iris germanica L. plant was determined after harvest. The results showed that the growth of Iris germanica L. was inhibited over 5 mg/kg Cd concentration, i.e., decreasing in the biomass, tiller number and leaf area. The flowering stage was prolonged under less than 10 mg/kg Cd concentration, while the extension of green stage was observed under less than 1 mg/kg Cd concentration. Cd stress reduced net photosynthesis rate and transpiration rate of Iris germanica L.. With increasing Cd concentration of the medium, root activity, chlorophyll and water contents all decreased, free proline and soluble sugar contents increased and then decreased, while the permeability of cell membrane ascended gradually. In the present study, the accumulator factor of Cd in Iris germanica L. was over 1.0, the accumulation of Cd in root of Iris germanica L.was greater than in shoot. Cd concentration in Iris germanica L. increased gradually with increasing Cd concentration of the medium, while accumulative factor and translocation factor decreased. The maximum accumulation of Cd in Iris germanica L. was 2.122 mg/plant at applied Cd level of 20 mg/kg. Cd stress suppressed cell differentiation, decreased the photosynthesis and transpiration, destroyed the internal environment of Iris germanica L.. The damage of Iris germanica L. at low Cd concentration was effectively alleviated by the accumulation of both free proline and soluble sugar. It could be concluded that Iris germanica L. was suitable for the remediation of Cd polluted soil when Cd concentration in soil was less than 5.0 mg/kg.