C17 effectively inhibits the growth of Arabidopsis on soil. A and B, Six-day-old Arabidopsis seedlings were grown on soil sprayed with a solution containing C17 (50 μm, 100 μm, and 200 μm; A) or isoxaben (0.5 μm, 1 μm, and 2 μm; B) or water containing solvent (0 μm). Scale bars, 1 cm.