Nitrogenase Activity, Nodule Respiration, and 02 Permeability Following Detopping of Alfalfa and

Gas exchange measurements and noninvasive leghemoglobin (Lb) spectrophotometry (nodule oximetry) were used to monitor nodule responses to shoot removal in alfalfa (Medicago sativa L. cv Weevichek) and birdsfoot trefoil (Lotus corniculatus L. cv Fergus). In each species, total nitrogenase activity, measured as H2 evolution in Ar:02 (80:20), decreased to 0.65 for a majority of nodules of each species. This increase could lead to 02 inactivation of nitrogenase.