A bisphosphonate increasing the shoot biomass of the metal hyperaccumulator Noccaea caerulescens

The feasibility of using the hyperaccumulator plant, Noccaea caerulescens, to remove trace elements from contaminated soils has been studied extensively. However, this plant creates too low biomass and an inappropriately slow growth rate for actual use in the field. Soluble bisphosphonates (BPs) are well-known pharmaceutical compounds e.g. affecting the osteoclast function in body through metabolic pathways. We devised an insoluble aminoBP, hydroxyundecylidene-1,1,-bisphosphonic acid with a long alkyl chain to be extremely effective metal chelator, and its possible use in phytoremediation deserves more attention. This article examines the effects of seven BPs on the shoot biomass, shoot metal concentrations and removal (Cd, Ni, Zn and Pb) by N. caerulescens in a pot experiment. The soluble BPs were incorporated into the soil in the irrigation water and the insoluble BP as solid after which the soil was spiked with metals. The insoluble aminoBP was found to considerably increase the shoot yield of N. caerulescens, especially in Ni-spiked soil, thus showing enhanced shoot Ni removal.