Acetylene reduction by roots and associated soil of New Zealand conifers

• Published in: Soil biology & biochemistry 1973, Vol.5 (1), p.171-179
• Main Authors: Silvester, W.B., Bennett, K.J.
• Format: Article
• Language: English
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/0038-0717(73)90107-7

An extensive survey of native conifers ( Dacrydium, Podocarpus, Libocedrus, Phyllocladus and Agathis spp.) showed that C 2H 2 reduction was often associated with their mycorrhizal short roots (‘nodules’). C 2H 2 reduction was associated with roots only if it also occurred in surrounding soil, but it could be found in soils and not in the root region. Over 50 per cent of the C 2H 2 reduction activity could be removed by washing roots in distilled water while complete loss of activity occurred when they were surface sterilized with hypochlorite solution. C 2H 2 reduction may also be associated with long roots of podocarps and roots of non-podocarp species. Fermenting and humifying horizons of forest soils showed much greater rates of C 2H 2 reduction than either mineral soil or roots. Results suggest that previous claims for nitrogen fixation by podocarp roots can be attributed to nitrogen fixation by bacteria in the root region rather than by endophytic organisms.