| Remediation of heavy metals polluted wetland was concerned by more and more scholars recent few years,and Phytoremediation of heavy metal polluted wetland had already turned into a new research field.Use of plants to remedy heavy metals polluted wetland,itself characteristic,biomass and tolerance of plants need to be considered, together with.accumulation capacity of the plants.Growth condition of Hedychium coronarium(HC),uptake and accumulation together with concentrating capability of copper in HC under copper stress were investigated in a pot culture of simulated wetland. The differential centrifugation technique and sequential extraction method were used to study the Subcellular distribution and the chemical forms of copper in leaves,stems and roots of the plants.In addition,ultra-structural changes in leaf cells of HC under 400 mg·kg-1 concentration copper stress were investigated with transmission,electron microscopy.The results were as follows:(1) When the treatment concentration of copper was 50 mg·kg-1,copper could promoted the growth of HC.As the concentration of copper increasing,symptoms of copper toxicity were showed gradually.The leaves of plants intenerated and curled,the color of the leaves turn from green to yellow,when the concentration of copper was 400 mg·kg<sup>-1,growth of parts of the plants were restrained,the leaves of the plants was shriveled,and he nether parts of stems began to rot and turn into brown.It came to the conclusion that 400 mg·kg-1 probably the critical concentration of copper toxicity in HC.(2) The accumulation of copper in HC increased with the increase of the concentration of copper,yet it was significantly different in different organs of the plants.When the concentration of copper was less than 150 mg·kg-1,the accumulation of copper in the plant was found in the order of root＞leave＞stem.While it was in the order of leave＞root＞stem when the concentration of copper was no less than 200 mg·kg-1.And it reached to the max accumulation contents 569.08 mg·kg-1,which was 2.5 times than contents of copper in roots. (3)When the concentration of copper was more than 150 mg·kg-1,biology accumulation coefficient and transfer coefficient of HC were both beyond 1.However because of the apparent symptoms of copper toxicity,the plants suffered from physiological hurt and death quickly,which was showed when the concentration of copper was 400 mg·kg-1,HC could not defined to be copper hyper-accumulation plant.Although HC was not satisfied with the standard of copper hyper-accumulation plant,the upper part of the plants had high accumulation of copper,the copper contents of which was from 29.5 times to 118 times than the common plant in which had 5-20 mg·kg-1 copper.It indicated that HC had certain copper tolerance.In addition,as the concentration of copper increasing,the transfer coefficient of HC increased gradually.When the concentration of copper was 400 mg·kg-1,the transfer coefficient come to 2.6.The higher was the transfer coefficient,the plants could easily transfer copper in polluted wetland to the upper parts themselves.Through several times planting and harvesting of the plants,the contents of copper in polluted wetland can decrease which indicate that HC have certain polluted wetland remedy potential.(4)In all treatments,the copper in leaf was mainly on cell wall and in soluble fraction, while relatively lower in cell organelle.The copper in the root was predominated with Ethanol- and water-extractable forms,while Nacl-extractable form was dominant in the stem.Whereas NaCl-,HAC- and HCl-extractable forms in the leaf,which were less active, were dominant.(5)Under 400 mg·kg-1 copper stress,obvious changes in the ultrastructure of leaf cell were observes with transmission electron microscopy.The osmiophilic granules evidently swelled and the chloroplast circular dilated with the structure of which was damaged.The damage of structure of chloroplast surely lead to the decrease of the absorbability of light, which would influence the normal photosynthesis in plants. |
