[Cytokinins in Helianthus annuus].

With two extraction procedures differing in the very first extraction steps two cytokinins from a total amount of 180 kg sunflower leaves could be isolated. One of these cytokinins is identified as zeatin by Rf values, UV absorption, melting point of its picrate and its biological activity. The same data are given for the other cytokinin, which is very probably ribosylzeatin. The total free cytokinin content of sunflower leaves is calculated to be 50-90 μg of kinetin equivalent, or 5-9 μg of zeatin, per kg of fresh leaves.Besides the leaf extraction, 100 l of root exudate of sunflowers were collected and the cytokinin was isolated. The root exudate contains 5-6 μg of kinetin equivalent, or 0,5-0,6 μg zeatin per 1 bleeding sap. The Rf values and UV absorption are similar to the corresponding data recorded for zeatin.