Phytoextraction by harvesting dead leaves: Cadmium accumulation associated with the leaf senescence in Festuca arundinacea
Abstract Phytoextraction strategy by harvesting dead leaves provides non-stop phytoremediation and a great saving in disposal cost of hazardous plant residues. This strategy is entirely dependent upon the amount of cadmium (Cd) accumulated in dead leaves. However, it is unknown that whether the leaf Cd accumulation is associated with its senescence and how to regulate its Cd accumulation. This study showed that Cd was preferentially and consistently distributed to and accumulated in the senescent leaves with the new leaf emergence and the old leaf dieback under 75 µM of Cd stress in tall fescue (Festuca arundinacea). Individual leaf monitoring from its emergence to senescence showed that Cd concentration increased exponentially with the leaf life cycle, while leaf biomass decreased gradually after 14 d of leaf emergence. The total amount of Cd accumulated in the leaf showed an exponential increase during leaf senescence, regardless of the leaf biomass loss. Our results demonstrated that leaf Cd accumulation was significantly associated with its senescence and the highest Cd accumulated in dead leaves could be contributed from the continuous Cd input during the leaf senescent process, indicating that further regulatory studies should be focused on the leaf senescence process to achieve higher Cd accumulation and phytoextraction efficiency by harvesting dead leaves.