ГЕНОТОКСИЧЕСКИЕ ЭФФЕКТЫ ДОННЫХ ОТЛОЖЕНИЙ РЕКИ ЧУМЫШ В КЛЕТКАХ КОРНЕВОЙ МЕРИСТЕМЫ ALLIUM CEPA L.

<p><em> </em></p><p>Cytogenetic effects of bottom sediments from Chumysh river near Talmenka (Russia, Altai Territory) were studied. It was found that the aqueous extracts of bottom sediments induced a strong cytotoxic effect reducing 1.7 times the mitotic activity in the apical root meristem in <em>Allium cepa </em>test system. The level of pathological mitoses (14.01%) was significantly higher than the background value (0.86%) and indicated the presence of factors with a total mutagenic activity in the bottom sediments of the river. This level is classified as high one. The different types of unequal chromosome segregation were the main violations during cell divisions. Dominance in the spectrum of anomalies metaphase spindle pathologies gave reason to believe about the chemical contamination of bottom sediments from Chumysh river. Stress factors of the sediments activate adaptive mechanisms of cells in test system to preserve their viability and reliability of the transmission of genetic information to future cell generations. The adaptive mechanisms are micronucleus and polyploidy cell formations.<em></em></p>

Number of nucleoli in diploids and polyploids of the genus Achillea L.

Nucleoli were counted in 9228 interphase nuclei of the apical root meristem of 40 <em>Achillea </em>L. taxa (di-, tetra-. hexa- and octoploids). It was established that the distribution of nucleoli number in an interphase nucleus can be used as a rough practical indicator to distinguish between diploids and polyploids. The highest number of nucleoli (12) was found in an octoploid <em>Achillea pannonica</em>, but only in a small percentage of the nuclei (0.3% out of 283 nuclei).

Genome Size Is a Strong Predictor of Root Meristem Growth Rate

Variation in genome size (GS) has been linked to several facets of the plant phenotype. Recently it was shown that GS is significantly correlated with cell size and the duration of the cell cycle. Here we test the hypothesis that GS might also be a predictor of apical root meristem growth rate (RMGR). We studied eight species of eudicots with varying GS using time-lapse microscopic image analysis. A significant negative exponential relationship was observed between GS and RMGR. Our results show significantly decreased RMGR for large genome species. This relationship represents a significant consequence of GS expansion in plants and may partly explain why genome sizes tend to be small in eudicots. Interestingly, parasitic plants, which do not rely on root growth as much, often have large genomes.