Purine alkaloid biosynthesis in young leaves of Camellia sinensis in light and darkness

The short-term effects of light on caffeine biosynthesis were investigated by feeding [8-C-14]adenine to young leaves of tea (Camellia sinensis L.). Light did not have any significant influence on the levels of radioactivity associated with the purine alkaloids. The long-term effects of light on caffeine production were studied using young shoots from plants that were maintained in almost complete darkness (1% full sunlight) by being covered with black lawn cloth. In the control shoots of the naturally-grown plants there were net increases in the total purine alkaloid contents of 2,430 nmoles shoot-l, while in shoots that had been in darkness for 7 days much lower increases, 564 nmoles shoot(-1), were observed. Caffeine synthase (CS) activity was 332+/-55 pkat shoot(-1) in light which is ca. 40% higher than the 237+/-37 pkat shoot(-1) in plants kept darkness for 7-days. However, a similar pattern of the metabolism of [8-C-14]adenine was observed in naturally-grown and dark-grown shoots. These findings indicate light is not essential for the biosynthesis of caffeine in young tea shoots. The lower net formation of caffeine in shoots maintained in darkness is an indirect consequence of the reduced growth rate of the young shoots in the absence of light.