[Action of deoxyuridine on the inhibition of the rhizogenesis and the hypocotyl growth observed in the presence of 5-bromodeoxyuridine in the cuttings of etiolated tomato seedlings].

1. At relatively low concentrations, UdR generally enhances the inhibition caused by 5-BUdR. When the concentration of UdR is progressively increased, an inversion of the effects of UdR is observed; this inversion may go as far as complete reversal of the inhibition caused by 5-BUdR in the case of hypocotyl growth. 2. The comparison of the effects of CdR with those of UdR in the presence of 5-BUdR makes plausible the hypothesis that CdR acts only after being deaminated in vivo to UdR. 3. A hypothesis is suggested to explain the particular shape of the curves of the action of UdR obtained in the presence of 5-BUdR.