The Activation of Metabolic Systems during Crown-gall Tumor-cell Formation.

The transformation of normal plant tissue into tumor tissue occurs in three steps, which have been designated conditioning, induction, and promotion.' Conditioning is accomplished by substances present in the wound juice; induction by a tumorinducing principle (T-iP) produced by virulent Agrobacterium tumefaciens grown in unheated plant juice; and promotion, by indoleacetic acid or its physiological equivalent. For carrot, complete conditioning requires 16-20 hours at 25° C.; induction, an additional 60-70 hours; and promotion, another 28-30 hours-a total of 104-120 hours is necessary for optimal transformation. Incomplete conditioning, induction, or promotion results in weakly growing tumors. If resulting tumor growth is submaximal because of the inability of the tumor cell to synthesize sufficient amounts of a necessary factor, supplements of the factor should increase growth. Rapidly growing tumors, receiving optimal transformation, should not be simulated by any growth factors. The experimental evaluation of this hypothesis2 is reported in this paper.