Root growth rate response to brefeldin A (BFA). (A) Exocyst mutants are hypersensitive to the root growth inhibiting effects of BFA at a concentration of 3.2 μM. (B) Root growth rate response to BFA normalized to the growth rate at BFA = 0. Normalized root growth rates of exocyst mutants are significantly lower than that of Col-0, at a BFA concentration of 3.2 μM (p < 0.001, t-test, n = 18-24). Bars = standard error.