Aluminium is essential for root growth and development of tea plants (<i>Camellia sinensis</i>)

Abstract

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. Structural 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mainly localized to nuclei in root meristem cells, but then gradually moved to the cytosol when Al³⁺ was subsequently withdrawn.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.