Heavy Metals Zn <sup> 2 + </ Sup> And As <sup> 5 + </ Sup> Poisoning Mechanism Of Water Peanut Callus

Heavy metal (HM) contamination in water became more and more serious due to industrial activities and agricultural practices. In this paper, therefore, compact-type growth of Alternanthera philoxeroides callus was cultured, which was also used as experim ental material. In this paper, Zn2+ and As5+ were selected as the stress factors, in order to study the toxicity mechanism of heavy metals on aquatic plants. The results show that:(1) Using this method,we could get more sterile product, in which explant was fistly sterilized with 70%C2H5OH for 30s,then with 2%NaClO for 15min and at last with 0.1%HgCl2 for 5 min.The callus induction rate reached up to the peak from cultured stem with buds on 1/2 MS medium with 6-BA(2.5mg/L)/and NAA(0.1mg/L).(2) This paper studied the toxic effect of various concentration of Zn2+(0,10,50,100,200mg/L) on the callus of Alternanthera philoxeroides and showed that the effect was weak with low concentration of Zn2+(10 mg/L). When the concentration of Zn2+ was lower than 50mg/L, the activities of SOD, POD and CAT and the content of soluble protein, free proline, GSH and AsA increased. However, when the concentration of Zn2+ was increasing, the content of Chlorophyll a, Chlorophyll b, free proline, GSH and AsA decresed; Three kinds of antioxidases diordered and they couldn't prevent the content of O2- and H2O2 from rising effectively. Due to that, the content of free proline and MDA rised significantly. Transmission electron microscope observation indicated that Zn2+ caused irreversible damage to the cell membrane system, especially chloroplasts, mitochondria, endoplasmic reticulum and nuclei. It was concluded that the death of Alternathera philoxeroides callus under Zn2+ stress was resulted from the destruction of physiological function and structural foundation, and the disorder of physiological metabolism. The lethal concentration scope should in 50-200mg/L.(3) The effect of As5+ gradient concentrtions(0,5,10,25,50mg/L) on the callus of Alternathera philoxeroides was also studied in the paper. The results indicated that content of Chlorophyll a, Chlorophyll b, soluble protein, MDA and free proline increased; CAT and POD activities were initially enhanced followed by a decline, while SOD activity decreased; The content of GSH and AsA increased at first and then decreased, while all of them were higher than the content of control. The lethal concentration of As5+ to Alternanthera philoxeroides callus based on the experimental results was 10-50mg/L.In conclusion, it shows a good consistency between the toxic effect of HM on the callus of Alternanthera philoxeroides and that on aquatic plants, that trace of HM pollution has no significant effect on the growth of callus, while when the concentration of HM increased the toxic effect become more and more obvious. The result can serve to the practical value of treating callus with HM and can be applied to the research of aquatic plants on water pollution control. And that was not all, we can greatly improve efficiency and cost savings as callus can avoid the impact of environments and can be produced in large quantities.