Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Influence of the form of nitrogen nutrition reductase activity in young black locust. | 782s Ann. Sci. For. 1989 46 suppl. 782S-785S Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Influence of the form of nitrogen nutrition on foliar nitrate reductase activity in young black locust Robinia pseudoacacia L. F. Boutekrabt and G. Pizelle Laboratoire de Physiologie Vegetate et Forestiere Faculte des Sciences BP 239 54506 Vandoeuvre-lès-Nancy Cedex Francqe Introduction Robinia pseudoacacia L. fixes dinitrogen in symbiosis with a specific rhizobium and as a nitrogen-fixing tree gives a litter with a low C N Moiroud and Capellano 1981 which favors nitrification Montagnini et al. 1986 . In the field black locust can therefore use both symbiotic and nitrate nitrogen. Data on the nitrate reduction in R. pseudoacacia are still very limited Aznadi 1984 . The present work examines the effects of the symbiotic and nitrate nitrogen nutritions on the leaf nitrate reductase activity and the distribution of this enzyme activity in young black locusts. Materials and Methods Young black locusts inoculated with a suspension of crushed nodules were grown on a nitrogen-free nutrient solution in a growth chamber. Nitrate nutrition of the nodulated plants was assured by the addition of 4 or 10 mM NaNO3 to the nitrogen-free solution. Nitrogenase N2ase activity was measured on intact plantlets by the acetylene reduction method. Nitrate reductase NR activity was measured in vivo on leaf disks diameter 12 mm . Two disks were vacuum infiltrated in 3 ml of M NaK phosphate buffer pH containing M KNO3 and Triton X-100 v v . After incubation for 1 h at 30 C in the dark NQ- was determined spectrometrically at 540 nm in the incubation medium. Results Presence of a constitutive leaf NR activity affected by the N2 ase activity The leaves of nitrogen-deficient plants had a notable NR activity considered as constitutive since it was not induced by nitrate Fig. 1 . This enzyme activity decreased to a minimum value 1 nmol NOj-mg-1 DW-h 1 when the N2ase increased .
