engleski

The appearance of vacuolar polyphenols in vegetative buds and developing needles of Norway spruce (Picea abies L. Karst.)

Background and Purpose: Previous investigations on the spruce vegetative bud structure and physiology as well as the needle development revealed that striking changes occurred concerning the quantity and quality of phenolic compounds. Moreover, the amount and organization of polyphenols were used to assess the stage of cytological injury of needles exposed to various environmental stress conditions. In our study we described organizational 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 and chlorotic current-year needles. Materials and Methods: The material for study were vegetative buds, four developmental stages of young needles (7, 11, 15 and 19 mm) and mature current-year needles. Plant material was fixed in glutaradldehyde, dehydrated and embedded in methacrylate resin for light microscopy or in Spurr resin for electron microscopy. light microscopy was performed using three μm-thick sections, stained with Toluidine blue O. For electron microscopy ultrathin sections were contrasted with lead citrate and uranyl acetate. Results: The analysis of vegetative buds showed the presence of polyphenols in the medulla and in the dermal layer and mid cortex of needle primordia. A wide variety of forms were observed: fine scatered particles, grains, globules, thick folded ribbon and homogenous mass filling 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 advenced 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 deposits or thick folded ribbon-like polyphenols. Conclusions: The appearance of polyphenols is subjected to organizational changes during needle development. The presence of polyphenolic substances in epidermal cells of young needles should be considered as protection against natural environmental radiation. It can be speculated that polyphenolcs in mesophyll cells serve as osmolitically active substances that affect the water potential of the vacuole and in this way influence cell elongation during needle development.

Picea abies; vacuolar polyphenols; needle development

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