Effect of 3 years' free-air exposure to elevated ozone on mature Norway spruce (Picea abies (L.) Karst.) needle epicuticular wax physicochemical characteristics

We examined the effect of ozone (O(3)) on Norway spruce (Picea abies) needle epicuticular wax over three seasons at the Kranzberg Ozone Fumigation Experiment. Exposure to 2 x ambient O(3) ranged from 64.5 to 74.2 mu-l O(3) l-1 h AOT40, and 117.1 to 123.2 nl O(3) l-1 4th highest daily maximum 8-h average O(3) concentration. The proportion of current-year needle surface covered by wax tubes, tube aggregates, and plates decreased (P = 0.011) under 2 x O(3). Epistomatal chambers had increased deposits of amorphous wax. Proportion of secondary alcohols varied due to year (P = 0.004) and O(3) treatment (P = 0.029). Secondary alcohols were reduced by 9.1% under 2 x O(3). Exposure to 2 x O(3) increased (P = 0.037) proportions of fatty acids by 29%. Opposing trends in secondary alcohols and fatty acids indicate a direct action of O(3) on wax biosynthesis. These results demonstrate O3-induced changes in biologically important needle surface characteristics of 50-year-old field-grown trees. Free-air ozone exposure induced changes in needle wax characteristics of mature Picea abies