2-BP treatment interfered with the dynamics of RabA4b-positive secretory vesicles. A. Distribution of RabA4b-positive vesicles in a growing root hair of 4 DAG RFP-RabA4b transgenic seedlings treated with DMSO for 2 hr. The arrowhead points at the base of the clear zone where RabA4b-positive vesicles form an inverted cone. Below is merge of fluorescence and bright field images. B-D. Distribution of RabA4b-positive vesicles in a root hair right after initiation (B), a growing root hair (C), or an arrested root hair (D) of 4 DAG RFP-RabA4b transgenic seedlings treated with 10 μM 2-BP for 2 hr. The arrows point at enlarged vesicles positive for RabA4b. Below are the merges of fluorescence and bright field images. E-F. RFP-RabA4b fluorescence was visualized in root hairs treated with DMSO (E) or 10 μM 2-BP (F) for 2 hr using time-lapse confocal fluorescence microscopy. Left-most are the bright-field images. The arrowhead points to the base of the clear-zone. The arrows follow the moving track of a single large vesicle over time. Bars = 7.5 μm.