用标记~(14)C的蛋氨酸、黄苷和7—甲基黄苷,进行示踪试验时,发现不仅在茶树,而且在咖啡树中,都是T—甲基黄苷为咖啡碱的合成先质,由T—甲基黄苷通过T—甲基黄嘌呤和可可碱转化到咖啡碱。在茶树中,T—甲基黄苷参入咖啡碱的速率(24小时后约55％),远高于咖啡树(8天后26％)。当标记的蛋氨酸饲喂茶树新梢时,在参入后的早期培养中,发现在T—甲基黄苷中有大量的放射活性(约占饲喂~(14)C的10％),后期培养中,几乎 Tracer experiments with methionine, xanthosine and 7-methylxanthine labeled with ~ (14) C revealed that T-methylxanthine was synthesized not only in the tea tree but also in the coffee tree as caffeine Quality, conversion of caffeine from T-methylxanthine by T-methylxanthine and theobromine. In tea trees, the rate of T-methylxanthine incorporation into caffeine (about 55% after 24 hours) is much higher than for coffee trees (26% after 8 days). When labeled methionine was fed on the shoots of tea trees, a large amount of radioactivity was found in T-methylxanthine (about 10% of the diet-administered (14) C) in the early culture after the introduction. In the later culture, almost