Use of DNA-specific stains as indicators of nuclei and extranuclear substances in leaf cells of the Middle Eocene Metasequoia from Arctic Canada

Abstract

For this study, we used leaves of fossilized Metasequoia nathorstii from the Middle Eocene sediments of the Axel Heiberg Island of the Canadian Arctic Archipelago, and the leaves of modern M. glyptostroboides collected from the garden of the Komarov Botanical Institute RAS. Feulgen staining of the Metasequoia fossil leaves revealed the preservation of Feulgen-positive, heterogeneously stained nuclear structures in the cells, similar to those in the cells of the modern plant. The nuclei were brown-red-stained, and the chromocenters were stained more intensely, suggesting that the general morphology of the cell nucleus was preserved and the aldehyde groups of the deoxyribose that were available to react with the Feulgen's basic fuchsin were preserved in the nuclear chromatin of the fossil plants. The additional staining of the preparations with the alcian blue and Ehrlich's hematoxylin displays the cell walls and the adjacent intracellular material that is colored from light to dark blue. Staining the preparations with dA + dT-specific fluorochrome DAPI induced a weak fluorescence of the fossil cell nuclei, indicating the presence of some dsDNA molecules in the Metasequoia fossil leaves.