Spindle microtubules and chromosome behavior in mitosis of Luzula luzuloides, a species with holokinetic chromosomes

The organization of spindle microtubules (MTs) was examined by light micros copy in mitotic cells of Luzula luzuloides, a plant with holokinetic chromo somes. Allium cepa cells were used as comparative material. Spindle structu re and mitotic chromosomes were studied using phase-contrast microscopy and confocal laser scanning microscopy (CLSM) following anti-alpha-tubulin lab eling and propidium iodide staining. The mitotic chromosomes of Luzula were rod-shaped and approximately similar in length, and did not possess primac y constrictions. Luzula chromosomes untreated with saturated solution of al pha-bromonaphthalene, aligned in the metaphase plate, could not be observed as individuals. Their anaphase movement was specific; the spindle attachme nt was not localized but evenly distributed along the poleward edge of the chromosomes so that the chromatids moved apart in parallel, not forming the classical V-shaped figures characteristic of monokinetic chromosomes. The spindle of Luzula was relatively short with distinct blunt poleward ends. M icrotubules were equally spread through the metaphase plate, indicating the holokinetic nature of Luzula chromosomes.