
%0 Journal Article
%A Langkamp, PJ 
%A Swinden, LB 
%A Dalling, MJ 
%T Nitrogen fixation (acetylene reduction) by <I>Acacia pellita</I> on areas restored after mining at Groote Eylandt, Northern Territory
%J Australian Journal of Botany
%D 1979/08/01
%V 27
%N 4
%P 353-361
%K 
%R https://doi.org/10.1071/BT9790353
%U https://www.publish.csiro.au/paper/BT9790353 
%X Factors affecting the reduction of acetylene to ethylene by nodules of Acacia pellita O. Schwarz were studied on 3-year-old trees in the field. The specific activity of rooted nodules (22.8 &#177; 3.3 nmol mg-1 fresh wt h-1) was greater than that of detached nodules alone (13.5 &#177; 2.1 nmol mg-1 h-1). Acetylene reduction started without a lag phase and remained linear for about 4 h. The apparent Km value for acetylene was derived to be 11.2 x 10-3 atm. Nodule material could be kept successfully without loss of activity when moist and shaded from direct sunlight for periods of up to 1 h. Acetylene reduction ceased when the assay temperature was 0&#176;C, activity increasing to 20.3 &#177; 2.3 nmol mg-1 h-1 at 22&#176;. The Acacia plants exhibited a diurnal cycle of nitrogen (acetylene) fixation; the greatest specific activity at midday was 27.7 &#177; 4.8 nmol mg-1 h-1 when the shaded soil temperature was 32&#176;C and photosynthetically active radiation was 2550 &#956;E m-2 s-1. By using a regression of nodule number per tree on stem diameter to obtain the total number of nodules per hectare, the total nitrogen fixation per wet season was estimated to be 12 &#177; 4 kg ha-1 where the planting density in the study area was 1110 trees ha-1. The work is discussed with reference to its implications for management of the restored areas and the role of acacias as nitrogen-fixing plants in the pre-mining native Eucalyptus tetrodonta open-forest. 
