| Abstrakt: |
Using root tips of Allium cepa as a model system, coumarin, 7-hydroxycoumarin, 4-hydroxycoumarin, psoralen, and xanthotoxin inhibited mitosis. 7-Hydroxycoumarin caused the most marked changes in karyokinesis, which led to chromatin condensation and shortening of chromosomes, as well as disorganisation of microtubules. Other coumarins influenced mostly cytokinesis, causing aberrations in fragmoplast formation and displacement of the middle lamella. The cell wall between sister cells was aberrant, with telophase bridges often occurring late in the post-telophase stage. In the cytoplasm, changes were noted in the mitochondrial structure, ER arrangement and separation of parts of the cytoplasm, in which autolysis was observed. After treatment with 7-hydroxycoumarin the ER became hypertrophic, with cisternae of the rough ER still narrow and arranged in complexes of parallel sheets. After treatment with the psoralens the ER dilated and fragmented into small vesicles. Swollen and dividing megamitochondria suggest that cells may be under stress from oxygen deficiency. [ABSTRACT FROM AUTHOR] |
