engleski

Vacuolar polyphenols in developing needles of spruce

Introduction: Previous investigations on the spruce vegetative buds structure and physiology as well as the needles development revealed that striking changes occured concerning quantity and the quality of the phenolic compounds. Moreover, the amount and organisation of polyphenols was used to asses a stage of cytological injuri of needles exposed to the various environmental stress conditions. In our study we described organisational changes of vacuolar polyphenols in vegetative buds, developing needles as well as in mature current-year needles. Also, we compared the appearance of polyphenolics in healthy looking and chlorotic current-year needles. Materials and Methods: The materials for study were vegetative buds, four developmental stages of young needles (7, 11, 15 and 19 mm) and mature current-year needles of Norway spruce (Picea abies L. Karst.). Plant material was fixed in glutaraldehyde, dehydrated and embedded in methacrylate resin for light microscopy or in Spurr resin for electron microscopy. Light microscopy was performed using three μ m thick sections, stained with Toluidine blue O. For electron microscopy, ultrathin sections were contrasted with lead citrate and uranyl acetate. Results: The appearance of the polyphenols is subjected to organisational changes during the needle development. Analysis of the vegetative buds showed a presence of polyphenols in the medulla and in the dermal layer and mid cortex of needles primordia. A wide variety of forms were observed: fine scattered particles, grains, globules, thich folded ribbon and homogenous mass filing up the whole vacuole. In the first two stages of developing needles polyphenols were detected in the epidermal and mesophyll cells, mostly in the form of thin ribbon at the periphery of the vacuole. More advanced developmental stages (15 and 19 mm) contained a granular form of polyphenols, besides the ribbon-like ones. Granulated form dominated in the healthy looking mature current-year needles, while chlorotic needles contained more abundant granulated deposits or thick folded ribbon-like polyphenols. The electron microscopy revealed that such thick ribbons are formed by fusing and clustering of the well abundant globules. Conclusions: It can be concluded that appearance of the polyphenols is subjected to organisational changes during the needle development. The presence of the polyphenolic substances in the epidermal cells of young needles should be considered as the protection against the natural environmental radiation. It can be speculated that polyphenols in the mesophyll cells are serving as osmotically active substances that affect the water potential of the vacuole and at that way influence on the cell elongation during the needles development.

vacuolar polyphenols; spruce; ultrastructure

nije evidentirano