The Tolerance Mechanism And Phytoremediation Potential Of Several Aquatic Plants On The Copper Tailing Leaching Liquid

Six species of water plants, Sagittaria sagittifolia L., Eleocharis tuberosa S., Typha orientalis Pres., Acorus calamus L., Iris pseudacorus L. and Pontederia cordata L. were selected as the material to study the tolerance and phytoremediation potential of these six species under the stress of copper tailing leaching liquid (Cu-TL). The results are as follows:(1) The effects of Cu-TL on the growth Cu accumulation and translocation of S. sagittifolia, E. tuberosa, T. orientalis, A. calamus, I. pseudacorus and P. cordata were studied by liquid culture. The results show that the plant height of E. tuberosa under the treatment of Cu-TL significantly increased16.29%than control. The aboveground part dry weight of A. calamus and underground part dry weight of E. tuberosa were significantly higher than those of control, while, the aboveground and underground part dry weights of other species were lower than those of the control. Cu contents in the aboveground part of S. sagittifolia, T. orientalis, I. pseudacorus and P. cordata were11.20%,48%,39.29%and18.87%, respectively, higher than control. However, Cu contents in the aboveground part of A. calamus and E. tuberosa were lower than that of CK by27.17%and15.56%. The results indicated that A. calamus and E. tuberosa were more tolerant to Cu-TL than other species, the limitation of Cu translocation to the aboveground part of A. calamus and E. tuberosa might be one tolerant mechanisms of Cu-TL stress.(2) The effects of Cu-TL on the physiological and biochemical response of S. sagittifolia, E. tuberosa, T. orientalis, A. calamus, I. pseudacorus and P. cordata were studied by liquid culture. The test results show that Chl-a, Chl-b, Chl (a+b) contents of6species of aquatic plants under Cu-TL stress were lower than that of control. O2·-content in the underground part of P. cordata was significantly lower than that of control and the MDA contents in aboveground part was significantly higher than that of control. SOD activities in aboveground and underground parts of S. sagittifolia were increased55.75%and224.48%, and the POD activity was significantly decreased. CAT activities in the aboveground parts of E. tuberosa and P. cordata increased significantly, while, CAT activity in the underground parts of P. cordata, significantly decreased. Pro contents in aboveground and underground part of E. tuberose decreased significantly, while, in the underground part of P. cordata, significantly increased. GSH contents in aboveground parts of S. sagittifolia and T. orientalis significantly increased; GSH and ASA contents in aboveground parts of A. calamus decreased significantly. The results indicated that different species have the different response to Cu-TL stress and antioxidant system in six species of aquatic plants played an important role in resistance to Cu-TL stress.(3) The effects of Cu-TL on the anatomical structure of S. sagittifolia and E. tuberosa were observed by optical microscope. The results show that the structure of root tip of S. sagittifolia under Cu-TL stress have little change compared with control, while, more starch grains were found in the cortex cells; the cross section shape of petiole was not as rule as that of control, the net air cavities were relatively fewer than control and the area of gas cavities were larger. The changes in the size of epidermal cells of S. sagittifolia were obvious and the vascular bundle sheath cells arranged irregularly and some air cavities were broken. Compared with the control, root hairs of E. tuberosa under Cu-TL treatment were more than control and endothelial cells arranged closely, cells are smaller and thicker cell walls. The cortical cell arranged loosely and air cavities with irregular shape were larger. The leaf epidermal cells were round and palisade tissues under the epidermis were similar with control, spongy tissue and the sheath cells volume of vascular bundle were smaller. The results suggested the tissue organization of E. tuberosa was less affected by Cu-TL.(4) The effects of cultivation of S. sagittifolia and E. tuberosa on the physical and chemical characters, Cu phytoextraction of Cu-TL medium were studied by liquid culture. The results show that the cultivation of S. sagittifolia could make the pH value of the medium with different content of Cu-TL lower, improve the dissolved oxygen (DO) in medium. With the increase of the contents of Cu-TL, the electrical conductivity of medium cultivated S. sagittifolia increased gradually and total nitrogen and phosphorus decreased. Cu contents in the aboveground part of S. sagittifolia increased first and then decreased, and in the underground part, increased. The medium with different content of Cu-TL cultivated E. tuberosa were neutral. With the increase of the contents of Cu-TL, the electrical conductivities of the medium with different Cu-TL contents cultivated E. tuberosa gradually increased too and total nitrogen contents decreased. Cu content in the underground part of E. tuberosa under100%Cu-TLtreatment significantly increased and was83.08%more than than that of control. Cu concentrationsin the pure Cu-TL cultivated with S. sagittifolia and E. tuberosa were61%and59%, respectively, lower than pure Cu-TL without cultivated any plants. The results indicated that S. sagittifolia and E. tuberosa were remediation efficiency of Cu-TL and could be used to remediate Cu contaminated water environment.