engleski

Histochemical observations on the needles of norway spruce (Picea abies L. Karst.) trees affected by cement dust pollution

The callose deposition, phenolics and starch grains appearance as well as the position and organisation of Ca-oxalate crystals in current-year spruce (Picea abies, Pinaceae) needles affected by cement dust were compared with not affected ones. Although without chlorotic symptoms, previously reported lowering of chlorophyll content indicated the altered physiological status of affected needles. Direct deposition of cement dust on the needdle surface caused the crystalline crusts formation. Necrosis of mesophyll cells walls, mostly, present near the stomata what is connected with dissolving of crusts caused by moisture giving the calcium hydroxide solution generally penetrating through the stomata. The abundant callose deposits detected with aniline blue were present in hypodermal layers of cells as grain-like forms in different size making a coat around the needle mesophyll as well as in cell walls of mesophyll cells proximate to hypodermis plugging the plasmodesmata. In correlation with callose deposition numerous Ca-oxalate crystals were observed in affected needles mostly appeared as druses when treated with sulphuric acid in fresh hand-made sections. Electron microscopy showed massive crystal aggregates placed between sclerotic parts of cell walls. Detection of polyphenolic substances with Toluidine blue O stain revealed abundant massive granulated tannin deposits in the vacuoles of mesophyll cells in affected needles. The occurrence of tannins in mesophyll cells near the necrotic areas was in the form of thick ribbon or the thin one, as well as a homogenous mass indicating more advanced stage of cell injury. Dust affected needles had bigger and more abundant starch grains. In conclusion, the observed changes in callose deposition should be considered as the protective event, while other histochemical alterations indicated the stress situation caused by a direct deposition of the alkaline dust.

Picea abies; needles; callose; calcium oxalate; polyphenolics; starch; cement dust

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