Ultrastructural changes in onion (Allium cepa L.) root tip meristem cells treated with Selol and sodium selenate (IV)

Abstract

Investigations on the antimitotic and anticancer effect of Selol have been carried out for more than a decade. In a previous work we analysed ultrastructural changes in onion root tip meristem cells (the Allium test), their division activity (the mitotic index), and proportion of division phases (the phase index). Our study revealed inhibition of cell divisions in response to both compounds; however, the effect of sodium selenate (IV) on cells was more toxic, involving frequent clastogenic aberrations. The aim of the present work was to compare the effect of both compounds (organic and inorganic), containing selenium with oxidation number at +4, i.e. Selol and sodium selenate (IV), on ultrastructure of plant cells of the Allium test, and their concentration in plant cells. Analysis of ultrastructural changes showed high toxicity of sodium selenate (IV), with degradation of cytoplasm, nucleus and cell organelles. Treatment with Selol did not cause such dramatic changes in ultrastructure. It resulted in gradual increase of heterochromatinization of cell nuclei and a change in their shape, correlated with increasing concentrations of Selol and incubation period. Additionally, a comparison of concentration of both compounds in Allium test cells showed that the organic form of selenium (Selol) penetrated them much more slowly than the inorganic one (sodium selenate (IV)). The results obtained indicate much lower toxicity of Selol than sodium selenate (IV), which supports the necessity of further investigations of this compound as a potential safe anticancer drug.