Arsenic and lead induced changes in the frond physiology and ultrastructure of Pteris multifida Poir

Changes in the frond physiology and ultrastructure of Pteris multifida Poir. were investigated under greenhouse conditions in response to application of arsenic (As) and lead (Pb). Various levels of As and Pb (0, As300Pb500, As600Pb1000 and As900Pb1500 mg kg^-1) were applied to the plants. An increasing As and Pb level, as well as a higher duration significantly inhibited plant growth and decreased chlorophyll contents and levels of soluble proteins (SP) as compared with the control. Meanwhile, the activitities of superoxide dismutase (SOD) and malondialdehyde (MDA), as well as content of ascorbic acid (AsA) increased under As300Pb500 treatment, whereas at higher As and Pb concentrations these indexes decreased as compared with the control. Under As300Pb500 treatment, the activity of peroxidase (POD) declined by 6.4%, whereas under As600Pb1000 treatment it increased significantly. The activity of glutathione (GSH) showed induction at lower concentrations of As and Pb, but declined at higher concentrations. ICP-MS analyses indicated that the concentrations of As in different tissues decreased in the order of pinnae >; petioles >; roots. With an increasing As and Pb level, Pb concentration in the plants rose accordingly, with roots taking up greatest Pb than pinnae and petioles. The bioaccumulation factors and translocation factors for As were all greater than 1, while those for Pb were all less than 1. Frond ultrastructural analysis revealed that the excessive As and Pb concentrations caused adverse effects especially on the nucleus, chloroplast and mitochondria in the cells. Our study suggested that As and Pb exerted the toxicity through inducing oxidative stress in P. multifida and a variety of mechanisms were involved in detoxification of As and Pb. Moreover, P. multifida had potential for use in phytoremediation of As-contaminated soils while its phytoremediation capability for Pb-contaminated soils was limited.