IN GROWING EPIDERMAL-CELLS OF RYE COLEOPTILES MICROTUBULES ARE ASSOCIATED WITH THE NUCLEI

The localization and pattern of microtubules in post-mitotic epidermal cells of coleoptiles of rye seedlings (Secale cereale L.) were examin ed by means of immune-fluorescence and confocal laser scanning microsc opy. In 2-day-old etiolated coleoptiles, which grow by cell elongation , microtubules (MTs) were associated with the nuclei of the cells. In growing 3- and 4-day-old etiolated coleoptiles cortical MTs were obser ved thar were arranged in parallel bundles oriented transverse to the axis of elongation. Cessation of coleoptile elongation was accompanied by a reorientation of the cortical MTs into an oblique and longitudin al direction. Our results support the hypothesis that in growing, non- dividing epidermal cells MTs originate at the nuclear surface or withi n the nucleus. This organelle may function as a major microtubule nucl eating center in the cells of the juvenile rye coleoptile.