Differential effects of ozone onin vivonitrate reduction in soybean cultivars. I. Response to exogenous sugars

摘要

Two cultivars of soybeans (Glycine max(L.) Merr.) differing widely in their resistance to ozone were exposed to 0.5ensp;mu;l/ℓ ozone for 2ensp;h in growth chambers.In vivonitrate reduction was depressed by more than 50 in the primary leaves of Dare, the ozone-sensitive cultivar, but was not significantly altered in Hood, the ozone-resistant cultivar. Sucrose, up to 1.5 (w/v), added to excised seedlings of the Dare cultivar during exposure to ozone eliminated the ozone depression ofin vivonitrate reductase activity and also reduced foliar injury. Addition of two glycolytic intermediates, glyceraldehyde-3-phosphate and fructose-1,6-diphosphate, to the infiltration medium recovered somein vivonitrate reduction in treated Dare leaves. The levels of extractable nitrate reductase and glyceraldehyde-3-phosphate dehydrogenase in the primary leaves of both cultivars were unaltered by ozone fumigations. These observations led to the conclusion that ozone depression ofin vivonitrate reduction is not due to ozone inactivation of nitrate reductase or of the enzymes coupling nitrate reduction to glycolysis, but may be caused by an inadequate supply of photosynthetic sugars. It was also noted that ozone depression ofin vivonitrate reduction only occurred with treatments which subsequently caused the development of visible foliar injur