Effect of Acidic Fog on Epicuticular Wax Layer and Water Status of Picea Abies Karst

Abstract

Experiments carried out with 5-year-old Norway spruce trees showed that acidic fog (pH 3) had a detrimental influence on the epistomatal and the epicuticular waxes. The wax layer of the “ph 3” treated plants was damaged and had a melted appearance whereas the neddle surface of the control trees that had received a fog of pH 5 showed a dense stand of small wax threads. Treatment with acidic fog of pH 3 caused a decreasing water holding capacity of these trees compared with those treated with control fog. The acidic treatment resulted in highter transpiration rates of the whole trees under water stress, in higher water loss of excised twigs, and in lower values of the xylem water potential during the day compared with the control fog of pH 5. The osmotic potential was not affected by the different fog treatments. It is suggested that decline symptoms, now widely found in Central Europa, are mainly caused by combined effects of acidifying pollutants in the atmosphere and unfavourable weather, e.g. periods of drought in summer and winter.