Accumulation and distribution of aluminium and other elements in tea (Camellia sinensis) leaves

Tea plants (Camellia sinensis) are well known for their ability to accumulate high concentrations of aluminium (Al). Aluminium distribution in tea leaves has been previously estimated on a qualitative basis using energy dispersive X-ray microanalysis (EDXMA). However, no comprehensive studies have been earned out to quantitatively determine the distribution of Al, especially in young leaves which are used for the manufacture of commercial tea. Cuttings of C. sinensis var. sinensis grown in acidic soil were collected and young and old leaves were used for analysis. Total Al concentrations in young and old leaves were 380 and 6866 μg·g^-1, respectively. The leaves were freeze-fractured and the quantitative distribution of Al and other elements such as Mg, Ca and K was determined using EDXMA. In the young and old leaves Al was found to be preferentially accumulated in the upper epidermis. In particular, Al was accumulated in the cell walls, which had significantly higher levels than the vacuoles of epidermal cells. The Al concentrations in the vacuole of mesophyll cells was found not to change significantly between young and old leaves. In contrast, a large increase in Al concentration was observed in the epidermal cell walls. Calcium was present in higher levels on the cell walls and also present as crytals in the spongy mesophyll tissue. In contrast, K and Mg were evenly distributed across the leaf. Copyright © 2003 INRA, EDP Sciences.