INFLUENCE OF SOIL ACIDIFICATION AND LIMING ON SELECTED ENZYMES OF THECARBOHYDRATE-METABOLISM AND THE CONTENTS OF 2 MAJOR ORGANIC-ACIDS OF MYCORRHIZAL ROOTS OF NORWAY SPRUCE (PICEA-ABIES [L.] KARST.)

Effects of soil acidification and liming on the activities of three en zymes of the carbohydrate metabolism and the quantities of two of the major organic acids of mycorrhizal roots of Norway spruce (Picea abies [L.] Karst.) were studied at Hoglwald Forest in southern Germany. The enzymes investigated were glucosephosphate isomerase, pyruvate kinase and 6-phosphogluconate dehydrogenase. The organic acids studied were citric acid and malic acid. Annual mean activities of the three enzyme s were equal in mycorrhizal roots of the humus and the upper mineral s oil. But in autumn and winter the activities of each of the three enzy mes were higher than in summer. Of the various soil treatments only so il acidification affected the activities of the three enzymes. It stim ulated activities by a factor of 1.5 in mycorrhizal roots of the humus but had no effect on mycorrhizal roots from the upper mineral soil. M ycorrhizal roots in the humus contained approximately 10 times more ci trate and two times more malate than mycorrhizal roots from the upper mineral soil (0-5 cm). In mycorrhizal roots from the humus citrate and malate were of similar concentrations. In mycorrhizal roots from the upper mineral soil malate was approximately four times more concentrat ed than citrate. In the humus the citric acid concentration of mycorrh izal roots decreased under soil acidification by a factor of 1.4 while it increased under liming and compensatory liming (acid irrigation af ter liming) by a factor of 1.5. Malic acid concentrations increased ex clusively under liming in mycorrhizal roots of the humus by a factor o f 1.3.