On the Putative Role of Microtubules in Gravitropism of Maize Coleoptiles

摘要

The antimicrotubular drug ethyl-7V-phenylcarbamate (EPC), at 1 to 10 mH, strongly inhibits gravitropism in coleoptiles ofZea maysL. Under the same conditions, phototropism remains essentially unimpaired. Propyzamide, a antimicrotubular drug specific for plant microtubules, at 0.02 to 0.2 mM causes qualitatively identical results, but to a weaker extent. Immunofluores-cence data show that even only partial elimination of cortical microtubules in the outer epidermis is correlated with complete inhibition of gravitropism. Phototropism can proceed to some extent even after complete removal of cortical microtubules. Together with previous work the data indicate a complex role of the microtubular cytoskeleton in gravitropism: (1) late transduction of both, photo- and gravitropism and (2) early transduction of gravity, possibly by perceiving and transducing pressure or displacement of statoliths.