Nitrogen fixing activity in warty lenticellate tree barks

Detached lenticellate warty bark of Inga laurina was first shown to develop acetylene reducing activity (ARA) (18 nmol C2H2red·g-1 (F.W.)·hr-1) after a few days' incubation with ambient air containing 0.10 atm C2H2. Similar N2ase development was found to occur with warty barks of many other plant species including 12 leguminous and 9 non-leguminous trees growing in wet tropical and temperate forests. Among them higher activities (>7 nmol C2H2 red·g-1 (F.W.)·hr-1) were recorded in Inga laurina, Cynometra ramiflora, Cassia siamea, Robinia pseudo-acacia, Albizia julibrissin in the leguminous plants, and Ilex crenata, Ilex pedunculosa, Rhizophora mucronata, Bruguiera gymnorrhiza and Mallotus japonicus in the non-leguminous plants. The development of ARA was often accelerated under lower pO2 (0.05 atm) and pC2H2 (0.05 atm). Complete replacement of O2 with N2 or Ar in the incubation atmosphere resulted in full suppression of the development of N2ase activity. When ARA measurement was made with intact barks of n...