Cytological changes in meristematic cells of Allium cepa L. root tip treated with extracts from callus of Catharanthus roseus (L.) G. Don.

The effect of an ethanolic extract from callus of Catharanthus roseus on Al lium cepa root cells divisions was investigated. Two lines: white and green callus, were established on solid B5 medium with IAA 1 mg/l and kinetin 0. 1 mg/l. The HPLC analysis of callus extracts showed the presence of indole alkaloids, however not known pharmacologically active alkaloids or derivati ves used in semisynthesis (vinblastine, ajmalicine, serpentine, yohimbine, vindoline and catharanthine) have been found. The ethanolic extract of C. r oseus callus inhibited the number of mitoses in Allium cepa root tip cells. Short (1-3 hours) treatment resulted in an increase in the index of late p rophases, with characteristic light spaces, and the index of metaphases wit h twisted chromosomes forming an equatorial plate or irregular structures o f c-metaphases. At the same time, the percentage of anaphases and telophase s decreased significantly. Longer treatment of the root tip inhibited mitot ic activity, stopping it completely already after 12 hours. Interphase nucl ei became at first denser and homogeneous, eventually their structure becam e partitioned into zones and formation of chromatin territories, with disti nct large nucleoli has been observed. Electron microscope observations reve aled well developed rough endoplasmic reticulum and thick, invaginating cel l membrane.