Cellular fine structures and histochemical reactions in the tissue of a cypress twig preserved in Baltic amber

A twig of a cypress plant preserved for ca. 45 Myr in Baltic amber was analysed by light and electron microscopy. Cross-sections of the whole plant showed an almost intact tissue of the entire stem and leaves, revealing, to our knowledge, the oldest and most highly preserved tissue from an amber inclusion reported so far. The preparations are based on a new technique of internal imbedding, whereby the hollow spaces within the inclusion are filled with synthetic resin which stabilizes the cellular structures during the sectioning procedure. Cytological stains applied to the sections reacted with cell walls and nuclei. A strong green auto-fluorescence of the cuticle and the resin canals in the leaves was observed. Transmission electron micrographs revealed highly preserved fine structures of cell walls, membranes and organelles. The results were compared with taxonomically related recent Glyptostrobus and Juniperus plants.