Study on the mechanism of cadmium resistance in Phragmites australis
芦苇抗镉污染机理研究

The influence of Cadmium (Cd) on physiolgical and biochemical growth parameters was studied to elucidate the mechanism of cadmium resistance in Phragmites australis. Cd levels in roots, rhizomes, stems and leaves increased with Cd pollution. The levels in roots were the highest, while that in leaves were the lowest. Using X-ray microanalysis revealed that Cd accumulated markedly in cell wall, cytoplasm, vacuole and intercellular space. A gradient of Cd levels occurred in different parts of root cortex cell with the sequence: intercellular > cell wall > vacuole > cytoplasm. Sequential extraction revealed that the ratio of Cd extracted from different extraction media was markedly different, of which NaCl extractable-Cd was dominant in both roots and leaves of P. australis. Cd-binding proteins were found in both; root and leaf after gel filtration chromatograph. The Cd-binding protein in root might be a polymer of phytochelatins. In addition, a new polypeptides was found under Cd pollution, and at the same time the other protein disappeared. And the experiments of BSO also proved the detoxification of Cd by phytochelatins. All the above results suggested that detoxification of Cd in P. australis may involve different strategies: retention in root, accumulation in intercellular, deposition on cell wall, compartmentalization in vacuole, insoluble Cd-binding components and Cd-binding protein.