Habituation in Nicotiana bigelovii tissue cultures: Different behaviour of two varieties

The exceptionally high capacity for transformation to autotrophyfor hormones (habituation) discovered in Nicotiana bigeloviiled us to a comparison of the responses of 2 varieties (quadrivalvisand bigelovii) to different hormone treatments applied to theirseeds. Hormones used were: kinetin (0.8, 1.6, 3.2 ppm), 2,4-D(0.1, 0.4 ppm), IAA (2 ppm) and NAA (1, 2, 4 ppm). Callus formation and habituation were scored after transferon minimal medium (without hormones) 3 months after sowing.Var. quadrivalvis showed a much higher ability to form callusbut the callus formed was autonomous in a lower percentage ofcases when IAA or kinetin treatment was considered. Analysisof auxin-like substances in leaves of the 2 varieties showeda higher content in N. bigelovii var. quadrivalvis. Data arediscussed with particular regard to their relevance to tumorousphenomena in plants. ¹ Publication No 52 of the Laboratorio di Mutagenesi e Differenziamento,C. N. R. (Received March 30, 1971; )