Fig. 3. Interphase microtubules in rsw7 root tip cells. (A-D) Confocal immunofluorescence micrographs of microtubules in fixed and immunolabeled 7-day-old root epidermal cells. (A,C) Wild type, (B,D) rsw7; top panels (A,B) grown at the permissive temperature (19°C); lower panels (C,D) grown at 19°C for 6 days and then exposed to the restrictive temperature (30°C) for 12 hours. Images representative of 6-10 roots, per treatment, examined in four different experiments. Bar, 5 µm. (E) Dose-response curve for root diameter as a function of concentration of two different microtubule inhibitors, oryzalin (circles) and RH-4032 (squares). Data presented as mean ± s.e.m. of three replicate plates. The x axis (concentration) is logarithmic. In the absence of inhibitor, the root diamater of rsw7 plants is significantly greater than that of the wild type because the rsw7 phenotype is partially expressed at 19°C (Wiedemeier et al., 2002).