Figure 1.

Isoxaben inhibits the deposition of cellulose microfibrils. Freshly isolated tobacco BY-2 protoplasts do not exhibit cellulose microfibrils when treated with Cellefluor (a). Microfibrils become visible within 15 min of culturing (b) and are pronounced by 45 min (c). When similarly treated protoplasts are exposed to 2.5 μm isoxaben, microfibrils are not visible by 30 min (d), and by 75 min only faint staining is observed (e). By 24 h the prominent fluorescing material is observed as bright aggregates (f). Bar = 4 μm.