Influence of the herbicide oryzalin on cytoskeleton and growth ofFunaria hygrometrica protonemata

Summary Protonemata ofFunaria hygrometrica were exposed to the herbicidal MT inhibitor oryzalin. A reduction of the growth rate together with a disturbance of oriented polar growth is observed. Both effects are reversible. Visualization of MT by IFT reveals differential sensitivities of MT. At lower concentrations (10^–6 M) only the cytoplasmic MT are depolymerized causing impairment of the migration of the nucleus and the transport of the plastids. Close association of MT with the surface of the plastids is demonstrated. At higher concentrations of oryzalin spindle and phragmoplast MT are affected as well. They are found in unusual orientations and display a variety of aberrant forms like multipolar spindles or the occurrence of several mini-spindles within one cell. The mode of action of oryzalin is discussed and the necessity of a continuous network of cytoplasmic MT between nucleus and growing tip for the maintenance of polar growth is emphasized.Abbreviations CIPC isopropylN-3-chlorophenyl carbamate - DAPI Diamidino-2-phenylindol - DMSO dimethyl sulfoxide - EGTA ethy-leneglycol-tetraacetic acid - FITC fluorescein isothiocyanate - IFT indirect immunofluorescence technique - IPC isopropylN-phenylcar-bamate - MSB microtubule stabilizing buffer - MT microtubule - MTOC microtubule organizing centre - Ph phragmoplast - PIPES piperazine-diethane sulfonic acid - S spindleDedicated to Prof. Dr. K. E.Wohlfarth-Bottermann on the occasion of his 65th birthday.