Toxic effects of cadmium on tall fescue and different responses of the photosynthetic activities in the photosystem electron donor and acceptor sides.

Tall fescue (Festuca arundinacea Schreb) is a turf grass species which is widely used for rhizoremediation of organic contaminants and shows notable prospects in heavy metal phytoremediation. In this study, different concentrations of cadmium ion (Cd) were applied to study toxic effects of Cd and responses of tall fescue by soilless culture. Tall fescue showed comparable high tolerance to Cd as Indian mustard (Brassica juncea L.). Additionally, the treatment with high concentration of Cd leaded to decreased chlorophyll contents, production of reactive oxygen species (ROS) and lipid peroxidation, as well as damage of cell membrane, necrosis and apoptosis in tall fescue roots, and toxicity of Cd on physiologic properties of tall fescue has been well discussed. Moreover, in photosystem II electron donor side, electron transport from oxygen evolution complex (OEC) to Yz residue of D1 protein was inhibited under high Cd treatments, which may be due to the Cd induced ROS production and the replacement of Ca in the core of OEC. In electron acceptor side, electron transport efficiency from quinone B to photosystem I acceptors increased under high Cd treatments, which may be an important response for plants against Cd toxicity and its mechanism needs our further study.