Distribution and metabolism of root‐applied cytokinins in Pisum sativum

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Abstract
When N6 [8–14C] furfuryladenine was applied to the intact root system of Pisum sativum L. cv. Meteor seedlings it was almost completely metabolised to other compounds within 24 h. Of the total activity recovered from the plants 94.5% was retained in the root system itself. 14C was recovered in a number of ethanol‐soluble compounds and in ribonucleic acid, deoxyribonucleic acid and protein fractions of roots, stems, leaves and axillary buds. In rapidly growing axillary buds released from apical dominance by removal of the shoot apex the combined nucleic acid fractions accounted for 63.3% of the total 14C recovered from these organs. Xylem exudate collected from decapitated plants 0 to 12 h after supplying N5[8–14C]furfuryladenine to the roots consistently contained a single major 14C‐labelled compound which, in three different solvent systems, had the same Rf values as a major endogenous cytokinin isolated from the xylem of unlabelled plants. The content of N6 [8–14C] furfuryladenine itself in the xylem exudate was always low and in some experiments it could not be detected.It is suggested that part of the label from N6 [8‐ 14CJfurfuryladenine taken up by the intact root system may have become incorporated in an endogenous cylokinin before export to the shoot.