IDENTIFICATION OF SOME MAJOR CYTOKININS IN PHASEOLUS-VULGARIS AND THEIR DISTRIBUTION

The determination of the various endogenous cytokinins and their distr ibution among organs is important in understanding their role in growt h and development in the intact plant. Cytokinins in young plants of P haseolus vulgaris were purified by immunoaffinity chromatography and H PLC, and characterised by UV spectra. Zeatin nucleotide (zeatin ribosi de-5'-monophosphate) and isopentenyladenine nucleotide (isopentenylade nosine-5'-monophosphate) were the most abundant cytokinins in all orga ns. Their identities were confirmed by GC-MS. The levels of zeatin, ze atin riboside, isopentenyladenine and isopentenyladenosine never excee ded 5% of the nucleotides, as assessed by a methodology that preserves cytokinin nucleotides. Three extraction methods were compared with qu alitatively similar results, though differing in their suppression of nucleotidase activity. Cytokinin nucleotide levels were greater in the stems and petioles than in the roots and leaves on a per gram fresh w eight basis, and were greater in the stems than in the other organs on a per plant basis. Levels of the zeatin and isopentenyladenine nucleo tides were about equal in the stems and leaves, but in the petioles th e zeatin nucleotide levels were about twice the level of isopentenylad enine nucleotide, while in the roots they were about half the isopente nyladenine nucleotide level. The importance of considering the cytokin in form is emphasised.