Abstract:

Aluminum toxicity is a major limiting factor affecting yield and quality of crops in acid soil. Camellia sinensis is an Al-accumulating plant grown healthily even in strong acid soil with high aluminum content. The study of the forms and accumulation of aluminum will be helpful to reveal the Al-toleranting mechanism of tea plant. In this paper, the content of Al³⁺ in tea plants was determined after Camellia sinensis wastreated for 50 d with different concentrations of Al³⁺ in culture solution. Besides, the forms of Al were analyzed in the roots, stems and leaves of tea plants by the nondestructive ²⁷Al NMR with high accuracy. The old leaves of tea plant were the major Al-accumulating organ, whereas, roots would take the position of it and accumulate more aluminum when the plant was treated with 2 mmol L^-1 Al³⁺. ²⁷Al NMR test showed that the dissoluble aluminum in tea root, stem and leaf existed mainly in the form of [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺(Al₁₃), whose chemical shift was 63×10^-6, and it was the first discovery in tea plant. Besides of Al₁₃, there were two weak absorption peaks of –0.38×10^-6 and –0.17×10^-6 in three organs tested, which wereundetected aluminum complexes. Other three complexes appeared in old leaf when treated by 5 mmol L^-1 Al³⁺, which were Al-oxalate (1:1), Al-oxalate (1:2), and Al-phosphate, and the chemical shifts were respectively 6.4×10^-6, 12.7×10^-6 and –6.2×10^-6. In summary, most of Al³⁺in tea plant exist in chelate complexes or organic matter, which can be considered as one of Al-accumulating and Al-tolerance mechanism of tea plant.

Key words: ²⁷aluminum NMR, Camellia sinensis, Aluminum accumulation