Physiological Responses And Accumulation Of Cadmium And Lead In Allantodia Chinensis (Bak.) Ching And Dryopteris Fuscipes C. Chr. In Cd-Pb Complex Stress

This paper is about the effects of Cd-Pb stress on Allantodia chinensis (Bak.) Ching and Dryopteris fuscipes C. Chr.,focusing on physiological responses of two fern species to different metal concentration and stress time of. cadmium and lead, as well as their accumulation situation. The results showed:(1).Under Cd -Pb stress, external form of A. chinensis and D. fuscipes changed to certain extents.The chief performance was characterized by the following aspects. With increase of concentration and prolonging of time, leaves faded green gradually, even died. The number of sproutd young leaves decreased. Plant grew slowly. Typical relation of dose/effect and time/effect occurred for the two ferns.(2).Analysis of physiological indices of A. chinensis and D. fuscipes under Cd-Pb metal stress indicated that ,chlorophyll contents in the two ferns decreasd significantly, and chlorophyll a/b ratio rised. Metal stress had a positive effect in lower concentration and a negative one in higher concentration in the activities of Superoxide Dismutase (SOD) and Peroxidase(POD), as well as the contents of Glutathione (GSH) and Ascorbic Acid (ASA). We concluded that A. chinensis had stronger resistance to Cd -Pb stress than D. fuscipes based on physiological indices.(3). In the early stages of Cd-Pb stress, cell ultrastructure of the two ferns were complete and unwounded. When the concentration increase to 1.2+1200mg/kg, chloroplast deformed obviously, chloroplast thylakoids became indistinct, and cell wall distorted. Organelles were degraded, nucleolus structures destroyed, and nuclear membrane blurred. Cells were plasmolyzed, and some black substance deposited on the cell wall.(4).By means of SEM-EDX, we found that A. chinensis and D. fuscipes had strong ability to enrich lead. Within certain concentrations of metals, Lead in the two ferns mainly concentrated on leaves and petiole. It is also clear that the organ with maximum ability of metal accumulating was leaves, while the organ with minimum ability of metal accumulating was roots. When the concentrtion increased to certain extents, the transporting ability of lead was weak. The two ferns were potential material for phytoremediation.