Biochemical and Ultrastructural Changes Induced by Lead and Cadmium to Crofton Weed (Eupatorium adenophorum Spreng.)

Crofton weed (Eupatorium adenophorum Spreng.) is an invasion in China and its spread speed rate has been faster than anticipated. Laboratory and greenhouse studies were employed to investigate the effect of heavy metal elements on several factors and the survivability mechanism of Crofton weed. Biochemical and ultrastructural methods revealed that this plant tolerated low concentrations of lead (Pb) or cadmium (Cd) individually or in combination as well, based on measurements of photosynthesis, the malondialdehyde and proline content, and the total electrolyte rate. After Pb, Cd or a mixture treatment, the total electrolyte rate, the malondialdehyde and proline content increased in Crofton weed, and leaves became darker than those of the control. Cellular ultrastructure observations showed that a cellular ultrastructure altered, including a thickened cell wall, chloroplast deformation, and damaged mitochondrial membrane. In addition, the activity of catalase, peroxidase and superoxide dismutase and the soluble protein content were affected after treatment with high concentrations of Pb, Cd or a combination. Taken together, these results suggest that Crofton weed has a high tolerance to Pb and Cd at low concentrations but becomes susceptible at high concentrations. These results may help control the environmental threat of Crofton weed or other invasive weed species.