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The effects of aluminium (Al) on telophase/cytokinetic root-tip cells of Triticum turgidum were examined, using tubulin immunolabeling and electron microscopy. In cells, which at the beginning of the treatment were at a transitional stage between anaphase and telophase, the transformation of the interzonal microtubule (Mt) system into a phagmoplast was delayed. In cells treated at a telophase/ cytokinetic stage, the lateral phragmoplast expansion towards the cell periphery was delayed or inhibited. Besides, in cells entering telophase through an abnormal mitosis, Al inhibited phragmoplast formation and induced the organization of atypical tubulin bundles. The latter formed a network around the reassembling polyploid nucleus. The Al-effects resulted in the disturbance of cytokinesis and the formation of binuclear or polyploid cells, which lacked typical Mts. Instead of them, the post-telophase cells displayed atypical tubulin aggregations. In addition, Al affects cell plate development. Dividing cells, encompassing early interphase daughter nuclei, contained incomplete, atypical cell plates. The latter were quite thick, wavy and perforated, showing large "islands", which contained electron transparent material. In some cells, the atypical cell plates gave rise to incomplete daughter walls, but in some others they were dismantled. The aberrant cell plates as well as the young daughter cell walls fluoresced intensely after aniline blue staining, an observation suggesting that they contain significant quantities of callose. The above findings combined with those derived from the study of the Al-effects on the mitotic spindle show that Mt cytoskeleton is a target site of Al toxicity in dividing cells. |
