Bioaccumulation of microcystin and its oxidative stress in the apple (Malus pumila).

The bioaccumulation and harmful effects of microcystins (MCs) and the activity of peroxidase (POD) and superoxide dismutase (SOD) were examined in the apple (Malus pumila) exposed in vitro with the crude extract of toxic cyanobacterial blooms from Dianchi Lake in southwestern China. The results showed that the growth and proliferation of M. pumila shoots in vitro decreased markedly after exposure to microcystins above 0.3 microg/ml. Recovered microcystins determined by enzyme-linked immunosorbent assay (ELISA) in M. pumila shoot cultures increased with exposure time and concentration. After 14 days exposure to the concentration of 3 microg/ml microcystins, M. pumila shoot cultures accumulated microcystins up to a concentration of 510.23 +/- 141.10 ng MC-LR equiv/g FW (fresh weight), equivalent to an accumulation rate of 36.45 ng/g day. POD activity was significantly increased after 7 days exposure to 3 microg/ml microcystins. After 14 days of exposure, microcystins caused POD to increase significantly at the concentration of 0.3 and 3 microg/ml. The activity of SOD was not affected by microcystins at concentrations up to 3 microg/ml on 7 days. After 14 days exposure to microcystins, SOD activity increased significantly at the concentration of 0.3 and 3 microg/ml in M. pumila shoot cultures.