Subcellular distribution and chemical forms of lithium in Li-accumulator Apocynum venetum

Apocynum venetum is a promising species to remediate an emerging environmental contaminant lithium (Li). However, no research has been conducted so far relating Li tolerance mechanism. In order to improve the understanding of Li transportation and detoxification, subcellular accumulation and distribution of different chemical forms of Li was studied in Apocynum venetum. Subcellular Li compartmentalization analysis showed that majority of Li was located in vacuole (45.52-72.65%) and cell wall (14.84-29.02%) under Li treatment. Furthermore, water soluble and ethonal extracted Li (inorganic Li) are the main chemical forms of Li taken up by A. venetum. With the increase of Li concentration in the medium, Li content in all subcellular fractions and proportion of F-ethanol form with high mobility increased. The greatest amount of Li was found in soluble fraction in leaves at 25 mg L^-1 Li treatment, followed by soluble fraction in leaves at 2.5 mg L^-1. These results suggest that Li compartmentation in leaf vacuoles is important in Li detoxification and Li accumulation of A. venetum.