Contrasting allocation of magnesium, calcium and manganese in leaves of tea (Camellia sinensis (L.) Kuntze) plants may explain their different extraction efficiency into tea.

During tea preparation mineral elements are extracted from the dried leaves of tea (Camellia sinensis (L.) Kuntze) plants into the solution. Micro-particle induced X-ray emission was employed to investigate the spatial distribution of magnesium (Mg), calcium (Ca) and manganese (Mn) in the young and old leaves of tea plants grown in the absence and presence of aluminium (Al) in the substrate. Results revealed that in tea leaves the largest concentrations of Mg occurred in the epidermis, of Ca in oxalate crystals and of Mn in epidermis and oxalate crystals; there was a leaf-age effect on tissue-specific concentrations of Mg, Ca and Mn with all tissues of old leaves containing larger concentrations of Mg, Ca and Mn than young leaves; supplementation of substrate with Al reduced concentrations of Mg, Ca and Mn in the old leaves, and a link between the distribution of Mg, Ca and Mn in the tea leaves with the extraction efficiencies of these elements into the tea was possible. We conclude that old leaves of tea plants cultivated under conditions of low Al availability will have the largest concentrations of Mg, Ca and Mn and may represent most acceptable ingredient for the preparation of tea. Image 1 • Spatial distribution of Mg, Ca and Mn was investigated in the young and old leaves of tea. • The largest concentration of Mg was found in epidermis of both young and old leaves. • Ca was mainly associated with oxalate crystals. • Mn was found in epidermis and in oxalate crystals. • High extraction efficiency reported for Mg and Mn may be related with their allocation to epidermis. [ABSTRACT FROM AUTHOR]