Stress Responses And Accumulation Of Cadium And Lead By Six Kinds Of Groundcover Plants

The pot experiment was adopted and the ornamental groundcover plants, containingHemerocallis fulva, Iris germanica L., Canna indica, Pennisetum clandestinum, M.sinensis,Kentucky Bluegrass were selected as test materials to study their responses and accumulationto Cd and Pb under five Cd concentrations (0.5,1,5,10and20mg·kg^-1) and Pbconcentrations (50,100,200,500and1000mg·kg^-1). In comparison, the same setup withoutCd and Pb addition was used as a control treatment. The experiment was conducted with acompletely randomized design. Some morphological indexes （plant height, leaf area, tillernumber, shoot biomass and root biomass）, ecological indexes（net photosynthesis rate andtranspiration rate） and physiological indexes （chlorophyll content, root activity, water content,contents of free proline and soluble sugar） were observed in green stage and flowering stageof plants.The distribution of Cd and Pb in plants were determined after harvest. The mainconclusions of the studyare as follows:1. The effect of low concentration Cd and Pb treatment on growth of plants was notobvious, however the growth of plants was hold when treated with high concentration Cd andPb, reduced their landscape and ecological benefits. The green and flowering stages ofHemerocallis fulva, Iris germanica L., Canna indica were prolonged when the plants weregrown at low concentration Cd and Pb.2. The sensibilities of the six plants to Cd and Pb are different during species. To ensurelandscape application of the six plants, inputs of Cd to soil roughly should not exceedHemerocallis fulva:1mg·kg^-1, Iris germanica L.:1mg·kg^-1, Canna indica:1mg·kg^-1,Pennisetum clandestinum:0.5mg·kg^-1, M.sinensis:0.5mg·kg^-1, Kentucky Bluegrass:1mg·kg^-1;inputs of Pb to soil roughly should not exceed Hemerocallis fulva:50mg·kg^-1, Iris germanicaL.:100mg·kg^-1, Canna indica:200mg·kg^-1, Pennisetum clandestinum:less than50mg·kg^-1,M.sinensis: less than50mg·kg^-1, Kentucky Bluegrass:50mg·kg^-1.3. With the increased concentration of Cd and Pb, the root activity,chlorophyll contentand water content decreased, free proline content and soluble sugar content increased firstthen decreased, while the permeability of cell membrane ascended all along and along. It isthus clear that Cd and Pb stress reduced tiller numbers of plants, decreased the photosynthesisand transpiration, destroyed the permeability of cell membrane of plants. The damage ofplants at low Cd and Pbconcentration was effectively alleviated by the accumulation of bothfree proline and soluble sugar.4. The distribution of Cd and Pb in plants were root＞shoot,with the increasedconcentration of Cd and Pb, Cd and Pb concentration in shoot and root ascended, accumulatorfacr and translocation factor decreased. The accumulation ability of six plants toCd, Pb was Canna indica＞Hemerocallis fulva＞Iris germanica L.＞Pennisetumclandestinum＞Kentucky Bluegrass＞M.sinensis..5. The characteristics of Hemerocallis fulva and Iris germanica L. to Cd, Pb were better,they were suitable to grown in city gardens and on road-sides in urban areas; Both thecharacteristics of Cd, Pb tolerance and accumulation in Canna indica were powerful. itssuitable to grown on main roadsides and industrial estates; the characteristics of Pennisetumclandestinum and M.sinensis. to Cd, Pb were normal and their ecological benefits werepowerful, they were suitable to grown in residential areas; simple turfgrass should be limiteduse in urban greening.