Cytoskeletal drugs and gravity-induced lateral auxin transport in rice coleoptiles

Gravity-induced events such as amyloplast sedimentation and lateral auxin transport were probed with cytoskeletal drugs in coleoptiles of rice (Oryza sativa L.). Amyloplast sedimentation was retarded by taxol. Lateral transport of auxin (H-3-indoleacetic acid) was strongly inhibited by EPC (ethyl N-phenylcarbamate), but only partially inhibited by taxol. 1 mM EPC reduced gravitropism while phototropism was not affected. The findings suggest that microtubules may transduce pressure or proximity of amyloplasts to the auxin exporter in the plasmalemma.