Effect of Pb stress on ultrastructure and physiological characteristics of Potentilla sericea

Potentilla sericea was employed as an experimental material in a pot experiment to study leaf ultrastructure and physiological characteristics under different gradients of lead stress. The results showed that the chlorophyll content under low concentration (600 mg·kg-1) of Pb stress first increased, and then decreased, with the increase in duration of treatment time, whereas high concentrations (600 mg·kg-1) of Pb stress showed a declining trend. The content of soluble protein was decreased. The MDA and free proline content all significantly increased. SOD activities first decreased, and then increased. With the increase of stress, the toxicity of lead to P. sericea seedlings increased. Under high Pb concentration (2 000 mg·kg-1), part of the cell membrane disappeared, the double membrane system of chloroplasts was destroyed, granum lamella was dissolved, mitochondrial vacuolization was serious, and the crest disappeared. These results showed that P. sericea is tolerant to lead up to concentrations of 600 mg·kg-1.