Effects of long‐term nitrogen dioxide fumigation and nitrate supply on nitrite and Leghemoglobin concentrations, pH, and nitrogenase activity of soybean root nodules

Abstract

Exposing 12‐day‐old soybean plants to 0.2 ppm nitrogen dioxide (NO2) for four weeks increased the nitrite concentration and acidity, and decreased the Leghemoglobin (LHb) concentration and the nitrogenase activity of root nodules. The supply of 1 mol.m‐3 nitrate to the roots intensified the nitrite accumulation, decreased the acidity of the nodules, and alleviated the inhibition of nitrogenase activity by NO2 fumigation. These results suggested that the inhibition of nitrogen (N2) fixation by N fertilizer supply might relate to the acid‐alkali balance in nodules.