Accumulation Of Cu～(2+) And Responses Of Physiological And Biochemical Functions In Two Submerged Macrophytes

Responses of antioxidant enzyme in plants to heavy metal and phytoremediation of heavy metal are increasingly concerned. At present, many researches concentrated on the effects of copper on antioxidant enzymes have been conducted at home and abroad, most of which were involved in the acute exposure at high dose. But it was rarely studied on the effects dependant on the low exposure concentration and the chronic toxicity to antioxidant enzymes. In the field of the phytoremediation of copper pollution, submerged macrophytes are focused less than the terrestrial plants.In this study, Ceratophyllum demersum L. and Cahomba caroliniana A.Gray were used as the test plant. The following two aspects were investigated in vivo methods: 1) The toxicity effects of Cu2+ on the three main antioxidant enzymes (including CAT, POD and SOD) of two submerged macrophytes were detected at different low doses and on the chronic exposure, in order to establish the dose-effect relationship and the time-effect relationship, and thereby acquire the toxicity threshold; and 2) With two submerge macrophytes throng cultured individual or combined on the chronic exposure, it was found on the BCF of copper and the influence of interspecific relationships to the submerge macrophytes resistance or bioconcentration. The objective in this study was to assess the potential bioremediation feasibility using these two macrophytes in the copper-polluted water. The main results and conclusions were as follows:1. For the acute exposure duration, there expressed the dose-thresholds and time-thresholds in the effects of Cu2+ on the activities of CAT, POD and SOD in two macrophytes. When the test species were exposed at low dose and for a short period, Cu2+ can stimulate activities of antioxidant enzymes. Once exceeding the thresholds, Cu2+ may inhibit enzymes activities. In the seventh day, a significant positive relationship was found between the highest inhibitory ratio of CAT, POD, SOD activity in C. demersum L. and concentrations of Cu2+. The threshold of the highestinhibitory ratio of CAT, POD, SOD in C. demersum L. were respectively 38.02-46.29%, 40.43 - 87.44%, 44.54-49.63%. C. caroliniana A. had a higher tolerance for Cu2+ than C. demersum L. The former could survive at 2 u mol/L Cu2+. but the latter only 0.2- 1 u mol/L.2. C demersum L. and C. caroliniana A. showed certain potential to accumulate Cu2+ in the polluted water. The leaves and stems of C. demersum L. may contain 137.8mg/kg (dry weight) of copper, so it can be served as hyperaccumulators of copper. C. caroliniana A. may contain 61.0 mg/kg of copper; C. demersum L. couldn't tolerate high lever of Cu2+. Moreover, its leaves tended to rapidly senescence and defoliated in copper treatment group. We suspected that C. demersum L. was inadequate used as a single bioaccumulator. While C. caroliniana A. could tolerate the higher lever of Cu2+, it is advised to be a better selection to phytoremediation. When the two submerge macrophytes were planted together in Cu2+ solution, the respective BCF of copper in two plants increased and the toleration of C. demersum L. was enhanced slightly.