Metabolism of C-zeatin in phaseolus embryos : occurrence of o-xylosyldihydrozeatin and its ribonucleoside.

The metabolism of trans-[8-(14)C]zeatin was examined in embryos of Phaseolus acutifolius A. Gray P.I. 321637 and Phaseolus coccineus Lam. cvs Scarlet Runner and Desiree. In both species zeatin was converted to ribosylzeatin, ribosylzeatin 5'-monophosphate, O-glucosyl-9-ribosylzeatin and the recently discovered O-xylosyl derivatives of zeatin and ribosylzeatin (Turner, JE, DWS Mok, MC Mok, G Shaw 1987 Proc Natl Acad Sci USA. In press). Two new metabolites, identified by enzyme degradation and gas chromatography-mass spectrography analyses as O-xylosyldihydrozeatin and its ribonucleoside, were recovered from P. coccineus embryos. From this and previous studies it may be concluded that the potential to form O-xylosyl derivatives of zeatin is present only in embryos of three Phaseolus species (P. vulgaris L., P. coccineus, and P. acutifolius), but not in P. lunatus L., while the reduction of the side chain is most prominent in P. coccineus.