The Study On Cd Effect Of Growth And Some Physiological Characteristics Of Populus Clones

Phytoremediation of cadmium-polluted environment has become the popular part in area of environmental and biological science. Nowadays, the research about the selection of plants for phytoremediation focused on the hyperaccumulator. However, this green technology has some disadvantages: small biomass, limited environments of growth and lack of variety resources. This research, aim at finding the potential of using poplar (Populus) phytoremediation, finding the poplar's resistence mechanisms to Cd, finding the Cd accumulation and distribution in Populus' organs and discussing the difference among the four Populus clones.The cuttings of four Populus clones, provided by Chinese Academy of Forestry, were used as experimental materials. The clones were cultured in the nutrition solution, and different concentrations of Cd were added into the solution for gradient treatments. The Cd effects on the plant growth, foliage photosynthesis, gas exchange and the activities of antioxidant enzyme were investigated. The Cd accumulation and distribution in organs of Populus and the Cd effects on the absorption and utilization of Mg, Mn, Fe in roots and leaves were also researched. The results obstained were summarized as follows:1. All Populus clones in the present investigation were found to be tolerant to Cd. All Populus exposed to 10μM Cd showed no significant reduction of cumulative shoot length and root length versus the control. Higher concentration (50～100μM) of Cd inhibited the growth of cultivars. The inhibition increased significantly with increasing Cd concentration.2. Cd accumulation, in all organs of the Populus clones, increased significantly with increasing concentration of Cd and treatment time. Populus had the ability to take up and accumulate Cd primarily in their roots, with lower concentrations in shoots. Cd concentrations in barks were significantly higher than in woods. Cd concentrations in young leaves were significantly higher than in old leaves of the Populus clones.3. Cd inhibited the absorption of Mg and Mn in roots. However, Cd could stimulate the absorption of Fe in roots. Moreover, Cd inhibited the absorption and utilization Mg, Mn and Fe in leaves. 4. Cd inhibited the photosynthesis of Populus clones. Cd showed no significant inhibition to net photosynthesis rate, stomal conductivity and transpiration rate versus the control, under 10μM Cd treatment. However, 50～100μM concentration of Cd inhibited significantly the photosynthesis and gas exchange.5. After 28d-treatment, the activities of POD, SOD, CAT in the leaves of 4 Populus clones were enhanced by 10～50μM Cd treatment. The activities of three antioxidant enzymes were declined at 50～100μM Cd treatment. The content of soluble protein declined with increasing concentration of Cd.6. P. cv. Zhonglin-46 and P. cv. Langfang No.4 showed stronger resistance, and P. cv. Qingyang showed more sensitivity to Cd.7. P. cv. Qingyang and P. cv. Xiaoyeyang had higher capacity for remedying the lower Cd polluted area, and P. cv. Langfang No.4 showed better ability to accumulate Cd under higher concentration of Cd. In conclusion, Populus could be used for remedying the environment polluted by Cd.