Influence of the Shading Culture on Catechin Composition in the Tea Leaves

Abstract

The influence of shading culture on the catechin composition in the tea leaves was examined.
During the developing period of the tea shoots, the tea plants were covered with several sheets of black net for 8-13 days. The light intensity under the shade was reduced to 1.6-6.4 percent of the open field. The shoots were plucked at different intervals from the shaded and the unshaded plots and subjected to the estimation of each catechin fraction.
As a result of shading, the yield of the plucked leaves and the content of total catechins decreased, however, a uniform tendency of decreasing in catechin content was not observed with each catechin fraction. The decreasing of the contents of (-) epicatechin and (-) epigallocatechin was characteristic of variation by shading. A significant difference of gallate content between the shaded and the unshaded shoots was not observed. In consequence, the tea shoots grown under the shade were rich in the proportion of (-) epigallo catechin gallate. After removal of the shade, a remarkable restoration of catechin content occurred quickly.
It seems that the results mentioned above involve a suggestion of the possible pathway of catechin formation in the tea leaves.