Saturday, 15 July 2006

Aluminum concentration and forms in tea (Camellia sinensis L.).

Masanori Okazaki, Arata Okuyama, Naoya Nakagawa, and Shoji Matsumura. Tokyo University of Agriculture and Technology, 2-24-16, Nakacho, Koganei, Tokyo, 184-8588, Japan

Drinking tea is familiar in the world. High aluminum concentrations and their forms in tea are interested from one of the view point of the causing factors for dementia and the Alzheimer disease. Tea plant shows anti-acid characteristics and called to be a hyper aluminum accumulator. The objective of this study is to show the aluminum concentrations and forms in tea plant under the different nitrogen applications. Tea plants, Yabukita and Meihoku variety, were cultivated in the field of Melanudands, which located in Fuchu, Tokyo, and in the green house, applied with the different nitrogen level of 0 to 1350 kg N ha-1. Tea plant organs were collected separately after the appropriate cultivation and total aluminum concentration in the different organs were determined by an atomic absorption spectrophotometer (Hitachi Z-5000) and their forms in hot water and inorganic acid solution extracts were determined by NMR (Jeol JNM-EX400). Exchangeable aluminum concentrations in soils increased with increasing nitrogen applications which caused the acidification of soils. Aluminum concentrations in tea plants grown in the field and green house increased with increasing nitrogen applications; 2400 to 6600 mg Al kg-1 in old leaves and 190 to 1100 mg Al kg-1 in young leaves. The young tea leave extracts with hot water gave no clear signal of Al3+. However, the old tea leave extracts with hot water showed the signal of aluminum-oxalate complex.

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