Seasonal changes in the ability of nitrogen uptake by young tea (Camellia sinensis L.) plants were examined in order to clarify the nitrogen requirement of tea plants. A fixted amount of ¹⁵N-nitrogen was applied to the potted plants grown in a vinylhouse without side cover in every months throuout the year. Seasonal uptake of nitrogen was evaluated by the monthly absorption of ¹⁵N by the plants. Translocation of the monthly-applied nitrogen to the nitrogen in the first flush shoots was also analyzed.
Nitrogen uptake increased from spring to summer and reached to the maximum at August, thereafter it gradually decreased. Rate of nitrogen uptake further declined toward the winter months and reached to the minimum at February. Rate of nitrogen uptake in February was approximately 30% of that in August. Active uptake of nitrogen resumed in spring. Seasonal changes in nitrogen uptake observed in the present study were closely related to the changes in air temperature.
Nitrogen applied after October was effectively translocated to the first flush shoots in next spring. Contribution of the monthly-applied nitrogen to the build up of the first flush shoots became larger as the time of nitrogen apllication came near the bud break. However, a considerable amount of nitrogen in the first flush shoots was also originated from that applied before the summer in the preceding year.

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A simple method of HPLC for the determination of catechins of tea was developed. The contents of major catechins in prized teas of the national tea competition held at 1994 was analyzed using this method. The contents of (-)-epigallocatechin and (-)-epicatechin of these prized teas showed remarkably lower values than those of commercially available teas.

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