Abstract
Different aluminum concentrations (5, 50, and 100 ?M), as well as different exposure times (24, 48, and 72 h), were applied to investigate cytogenetical alterations in sunflower ( Helianthus annuus L.) meristem cells. Nucleolin was also examined under aluminum stress using silver-staining method and indirect immunofluorescent method. Results showed that the mitotic index decreased progressively when either aluminum concentration or exposure time increased. C-mitosis, anaphase bridges, and chromosome stickiness were observed in the aluminum treated root tip cells. Some particulates containing the argyrophilic NOR-associated proteins were distributed in the nucleus of the root-tip cells, and the amount of this particulate material progressively increased with increasing exposure time. Finally, the nucleolar material was extruded from the nucleus into the cytoplasm. The result also indicated the nucleolar protein nucleolin was translocated from nucleolus to nucleoplasm and cytoplasm, that presence of 50 ?M of aluminum for 48 h, suggesting that aluminum disturbed rRNA synthesis and induced the abnormal cellular location of nucleolar protein. The strongly toxic effect of aluminum on the nucleolus can inhibit or stop mitosis, and consequently inhibit root growth.