Buds longer than 1.5 mm at excision become unresponsive to inhibition by 1 μm NAA (a). Inhibition of lateral buds by NAA in the apical media block is dose-dependent (0.1–10 μm) (b). Other auxins supplied apically also inhibit bud outgrowth (c). Data shown are means ± SE (n = 10–15).