Figure 1.

Effect of detopping on nitrogenase activity in alfalfa nodules. Total nitrogenase activity was determined as peak H₂ evolution rate in Ar:O₂ (80:20, v/v). Data are expressed as percentages of the initial peak activity (total nitrogenase activity) before detopping. Data represent the means ± se of six replicates for the control and nine replicates for the detopped plants. The average total nitrogenase activity value before the detopping treatment was 100.6 ± 17 μmol H₂ g⁻¹ nodule dry weight h⁻¹ (n = 15).