USE OF 15N IN THE STUDY OF FIXATION OF ATMOSPHERIC NITROGEN BY NON- NODULATED SEED PLANTS
Both from observation of non-leguminous plants growing under natural conditions and also from measurements made of plot experiments with grasses it has been found that large amounts of nitrogen, of the order of 50-lb N/acre/year, accumulate both in the soil and in plant material. Measurements of the contribution made by nonsymbiotic nitrogen-fixing bacteria are only of the order of 2 to 3 lb N/acre/year, so that it appears likely that some other mechanism operates which leads to fixation of nitrogen with the growth of many nonleguminous plants. Experiments were carried out with the following species which grow well in New Zealand under poor nutrient conditions, especially as regards nitrogen: Pinus radiata, Coprosma robusta, Epilobium erectum and Dactylis glomerata. Plants have been grown in sand watered with a nitrogen-free nutrient solution when they have shown signs of nitrogen starvation, but, nevertheless, they have made considerable growth. Some plants have been exposed to an isotopically enriched atmosphere for periods of 7 to 14 days, and significant amounts of nitrogen-15 have been recovered from the combined nitrogen in the plants indicating that fixation of molecular nitrogen has occurred. The effect is not due to any of the known nonsymbiotic nitrogen-fixing bacteria which were shown to be absent from the sand cultures. Two possible explanations considered are that the effect may be due to microorganisms present in or on the plants, and that the effect may be due to some activity of the plants themselves. (auth)
- Research Organization:
- Victoria Univ., Wellington, N.Z.
- NSA Number:
- NSA-13-006217
- OSTI ID:
- 4270696
- Report Number(s):
- A/CONF.15/P/1507
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-59
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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