Needle mesophyll cell ultrastructure of 1st to 9th yr needles from Norway spruce (Picea abies (L.) Karst.) trees of different ages was studied at three different sites to determine the normal features of needle ageing, and the impact of air pollution on the needle ageing process. The sites included one rural area and two industrial environments, of which one contained SO2 emissions and the other SO2 and F emissions. The ultrastuctural features of needle mesophyll cells of different ages were found to be remarkably similar when young (20-yr-old) and mature (> 50-yr-old) trees were compared. Senescence-related ultrastructural symptoms such as increase in the number and size of plastoglobuli and an increase in the large lipid accumulations were observed with increasing needle age. In addition, the occurrence of lipid bodies in the central vacuole and an increased number of dark grains in the cell wall were detected in ageing needles. No changes in chloroplast length were observed during the ageing of needles, although the width of the chloroplasts showed a tendency to increase. A poor differentiation of granal membranes and an increase in small cytoplasmic lipid bodies and irregularly-shaped lipid material were symptoms typical of needles in the industrial areas. The ageing symptoms appeared in younger needles and were more evident in industrial areas than at the control site, suggesting an accelerated ageing process in the industrial areas.
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