Aluminium is essential for root growth and development of tea plants(Camellia sinensis)^∞

On acid soils,the trivalent aluminium ion(Al3+)predominates and is very rhizotoxic to most plant species.For some native plant species adapted to acid soils including tea(Camellia sinensis),Al3+has been regarded as a beneficial mineral element.In this study,we discovered that Al3+is actually essential for tea root growth and development in all the tested varieties.Aluminum ion promoted new root growth in five representative tea varieties with dose-dependent responses to Al3+availability.In the absence of Al3+,the tea plants failed to generate new roots,and the root tips were damaged within 1 d of Al deprivation.Struc-tural analysis of root tips demonstrated that Al was required for root meristem development and activity.In situ morin@staining of Al3+in roots revealed that Al mainly localized to nuclei in root meristem cells,but then gradually moved to the cytosol when Al3+was subsequently withdrawn.This movement of Al3+from nuclei to cytosols was accompanied by exacerbated DNA damage,which suggests that the nuclear-targeted Al primarily acts to maintain DNA integrity.Taken together,these results provide novel evidence that Al3+is essential for root growth in tea plants through maintenance of DNA integrity in meristematic cells.