Oxygen partial pressure as affecting nitrogen fixing activity in warty tree barks

Oxygen partial pressure as affecting nitrogen-fixing activity of warty lenticellate tree barks was investigated with detached barks of Mallotus japonicus Lindl. and Ilex pedunculosa Miq. Fresh bark pieces were incubated under atmosphere containing 0.1 atm C2H2 and varied concentration of O2. ARA of the tissue and pO2 in the vessel atmosphere were measured concomitantly over the incubation period. Results showed that ARA of the tissues only developed when pO2 in the vessel atmosphere was below 0.06 atm. The opt. pO2 for full operation of ARA lay at 0.03–0.05 atm.