Kinetics of Endogenous Cytokinin, IAA and ABA Levels in Relation to the Growth and Morphology of Tobacco Crown Gall Tissue

The kinetics of endogenous cytokinin, IAA and ABA levels duringthe growth cycle of a wild-type tobacco crown gall (W₃₈-B₆S₃)were compared with that of a shoot-inducing (Shi^-) mutant. Inboth tumor types, high IAA and cytokinin (essentially ribosyl-trans-zeatinand its corresponding glucoside) levels were built up by theend of the linear growth phase and maintained during the greaterpart of the exponential growth period. The stationary phasewas preceded by a very drastic decrease in the endogenous levelof both hormones. Quantitatively, the wild-type tumour showed a higher IAA leveland a reduced cytokinin level compared with the Shi^- mutant.No significantly different endogenous ABA pattern was observed.The reduced cytokinin level might correspond to the ratio oftransformed/untransformed cells in the wild-type tumour whereasthe reduced IAA level in the Shi^- mutant may be correlated withthe deletion of gene 2 in the T-DNA of the pGV 2206 Ti plasmid. The elevated cytokinin/IAA ratio induced shooting mainly ofthe untransformed cells in the Shi^- mutant tissue whereas inthe wild-type, the shoot suppression was compatible with thereduced cytokinin/IAA ratio. ⁴Senior Research Associate Nationaal Fonds WetenschappelijkOnderzoek (N.F.W.O.).⁵Research Associate N.F.W.O.⁶Recipient of an Instituut voor Wetenschappelijk Onderzoek inNijverheid en Landbouw grant. (Received February 23, 1984; Accepted June 19, 1984)