Influence of soil acidification and liming on selected enzymes of the carbohydrate metabolism and the contents of two major organic acids of mycorrhizal roots of Norway spruce (Picea abies [L.] Karst.)

摘要

The effects of soil acidification and liming on the activities of glucosephosphate isomerase [glucose-6-phosphate isomerase], pyruvate kinase and 6-phosphogluconate dehydrogenase (of carbohydrate metabolism) and the contents of citric acid and malicacid in the mycorrhizal roots of Picea abies, were studied at Hoglwald Forest in southern Germany, during 1990-91. Six plots were established in 1984 and consisted of 3 unlimed and 3 limed (4 t/ha dolomite) plots. For both treatments, one plot was irrigated with rainwater and one with acid rainwater (May 1986 to October 1990). Annual mean activities of the 3 enzymes were equal in the mycorrhizal roots of the humus and the upper mineral soil. However, during autumn and winter the activities of each enzyme were higher than in the summer. Of the various soil treatments only soil acidification affected enzyme activity by stimulating activities by a factor of 1.5 in mycorrhizal roots of the humus. Acidification had no effect on the mycorrhizal roots from the upper mineral soil. Mycorrhizal roots in the humus contained approximately 10 times more citrate and twice as much 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 4 times more concentrated than citrate. In the humus soil layer the citric acid concentration of mycorrhizal roots decreased under soil acidification by a factorof 1.4 while it increased under liming and compensatory liming (acid irrigation after liming) by a factor of 1.5. Malic acid concentrations increased exclusively under liming in mycorrhizal roots of the humus by a factor of 1.3.