Determination of nitrogenase activity in nodules
Nitrogenase activity was quantified using the acetylene reduction method
by Fishbeck et al.
(1973)
with slight modifications. Fresh soybean nodules (0.2g) were picked and
transferred to 25 ml rubber-sealed glass bottles filled with a mixture
of acetylene and air (v: v = 1: 100). The bottle was incubated at 28°C
for 2 h, and then the ethylene content was measured using a gas
chromatograph system (Trace GC Ultra, United States).