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

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