Effects of SO2 on the concentrations of carbohydrates and secondary compounds in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings

Abstract

Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings of open‐pollinated progenies and clonal cuttings were exposed to various concentrations of SO2 (50–155 nl l−1) in several growth chamber experiments. No visible foliar injury was observed in any SO2 exposure. The total sulphur concentrations of the exposed needles were significantly greater than in the control needles. Exposure to SO2 (100 and 155 nl l−1) reduced concentrations of glucose and fructose and increased concentrations of sucrose in pine needles. By contrast, one spruce clone had more glucose and fructose and less sucrose in needles exposed to SO2 (100 nl l−1), but in other spruces of clonal or open‐pollinated progenies no changes in sugar concentrations were detected in different SO2 exposures (50–155 nl l−1). Exposure to SO2 had no effects on concentrations of individual or total monoterpenes in pine or spruce needles. Concentration of total resin acids was significantly smaller in needles exposed to the greatest concentration of SO2 (155 nl l−1), but no changes were detected in other exposures (50–150 nl l−1) in either tree species. Concentrations of minor individual resin acids, palustric and neoabietic acids, were also affected by SO2 in needles of pine (155 nl l−1 SO2) and clonal spruces (100 nl l−1 SO2). Exposure to SO2 did not affect foliar concentration of total phenolics in pine and spruce seedlings. In exposure to 0, 50, 100 and 150 nl l−1 SO2, total phenolic concentration of spruce roots was increased linearly with elevated SO2 exposure level. By contrast one spruce clone had decreased concentrations of phenolics in roots after exposure to 155 nl l−1 SO2. The present results suggest that in conifers the response of carbohydrate and secondary metabolism to SO2 varies with the origin of tested seedlings and the SO2 concentration. Therefore, generalizations about the SO2 effects on suitability of food quality for folivorous herbivores are difficult to draw, except that a better supply of sulphur will be available from SO2 exposed seedlings. Copyright © 1995, Wiley Blackwell. All rights reserved