Flavanols and Flavonols in the Nuclei of Conifer Genotypes with Different Growth

Flavanols and flavonols of mitotic and post-mitotic nuclei in needles of Taxus baccata L., Tsuga canadensis L., and slow growing dwarf genotypes of both genera are investigated histochemically. The flavanols of nuclear chromatins and in the vacuoles stain blue with the p-dimethylamino-cinnamaldehyde (DMACA) reagent. Flavonols do not react with the reagent but owing to their UV absorbance they can be seen as bright yellow pigments. The nuclei in the photomicrographs obtained by microscopy were measured for flavanols at 640 nm. The vigorously sprouting Taxus baccata L. displays the most rapid cell cycling of the needles and the nuclei reveal clear blue and white mosaic structures. The flavanol component of Taxus baccata nuclei remains relatively stable most of the growing season. The dwarf genotypes also display fairly blue stained meristematic nuclei during the intense spring flush. However, after the spring flush and towards mid-summer the nuclear flavanols slowly decrease in parallel with a gradual increase in yellow staining nuclear flavonols. A mixture of blue stained flavanols and yellow flavonols results in greenish coloration of the nuclei. The greenish tint becomes more pronounced when the parenchyma cells mature and age. At the same time, the cytoplasm of the dwarf genotypes also begins to attain a more yellow tint. This trend continues towards mid-summer and autumn, particularly in the nana genotypes. It would appear that the yellow staining flavonols are linked to restricted growth conditions. In the present study, it becomes evident that the species-typical endogenous growth potential is related to both flavanol and flavonol allocation into the nuclei. The vigorously growing species of Taxus and Tsuga have a higher capacity for recruitment of flavanols into the nuclei than the very slow growing dwarf species.