IAA concentration(mg/ml) 0.0 0.005 0.03 0.18 1.08 3. 0.0 目 0.2 A89 FIGURE 21.13 The regulation of growth and organ formation in cultured tobacco callus at different concentrations of auxin and kinetin. At low auxin and high kinetin concentrations (lower left) buds developed. At high auxin and low kinetin concentrations (upper right) roots developed. At intermediate or high concentra tions of both hormones(middle and lower right) undifferentiated callus developed.( Courtesy of Donald Armstrong. Figure 10-7Figure 10-7