ENERGY AND REDOX STATUS, AND CARBON ALLOCATION IN ONE-YEAR-OLD TO 3-YEAR-OLD SPRUCE NEEDLES

Metabolite pools were determined in lyophilized homogenates of one- to three-year-old needles from 13-year-old spruce trees. These were exposed in open-chambers for five consecutive years to SO2 (30-mu-g m-3) and O3 (50 to 180-mu-g m-3), singly and in combination. The samples were taken shortly before bud break (mid-March). The energy (ATP/ADP) and redox status (NAD(P)H/NAD(P)) increased with needle age. This increase was most pronounced in needles exposed to both pollutant gases. To evaluate carbohydrate metabolism, levels of starch, sugars (sucrose, fructose, glucose), sugar phosphate (dihydroxyacetone phosphate, glyceraldehyde 3-phosphate (triose phosphates, TP), fructose 6-phosphate, fructose 2,6-bisphosphate: F2,6BP) and 3-phosphoglyceric acid (PGA) were measured. The concentrations of starch, glucose, fructose and TP on a dry weight basis increased with needle age, while those of sucrose and F2,6BP decreased. Interestingly, the total amount of soluble sugars remained constant in needles from control chambers and large fluctuations mainly occurred after a single application of the pollutants. Needles from fumigated trees generally showed somewhat lower starch and sugar, and fructose 6-phosphate levels. The content of TP increased with needle age while that of sucrose and F2,6BP decreased. This inverse behavior was even more prominent in the presence of both pollutants and is discussed in the context of recent knowledge on the regulation of carbon partitioning. There was a significant increase in the ratio of TP/PGA in samples from the combined exposure treatments. This also indicates an increase in the redox charge and corroborates the data on both the redox status of the pyridine nucleotide system and the significantly increased ATP/ADP ratio. The results are indicative of a switch in metabolism, from anabolic to predominantly catabolic reactions, which is most pronounced in the samples fumigated with both O3 and SO2. The data are compared to those obtained from naturally exposed trees in the southern Black Forest (Kalbelescheuer/Haldenhof, near Freiburg, Germany).