Growth regulators, Rhizobium and nodulation in peas : The cytokinin content of a wild-type and a Ti-plasmid-containing strain of R. leguminosarum.

The cytokinin content of roots and nodules of pea and the culture supernatants from two strains of Rhizobium leguminosarum has been examined. Roots, nodules and wild-type Rhizobium culture medium contained very little cytokinin as indicated by bioassay. Chemical ionisation gas chromatography-mass spectrometric analysis of the isopentenyladenine content of the culture medium from the Rhizobium strains confirmed that the content of the wild-type was low (approx. 1 ng dm(-3)) but that it was increased by the introduction of the Agrobacterium Ti plasmid into the Rhizobium strain.