Studies on phloem exudation from Yucca flaccida Haw. XIII. Evidence for the occurrence of a cytokinin nucleotide in the exudate

Phloem exudate of Yucca was analysed for cytokinin activity. Aftei partition in a water- and butanol-1 fraction, almost no cytokinin activity was found in the butanol phase (cytokinin base and nucleosides). Application of alkaline phosphatase to the water layer gave rise to a strong positive cytokinin response with the soy-bean callus test, an amount of approximately 520 ;j.g zeatin equivalent per litre being found in the exudate after treatment with alkaline phosphatase. The results indicate that a cytokinin, presumably zeatin, is translocated as a nucleotide.