Comparison of N{sub 2}-fixation measured with acetylene reduction and {sup 15}N dilution techniques in Gliricidia sepium seedlings grown under varying CO{sub 2} temperature and soil nitrogen
- Duke Univ., Durham, NC (United States)
The acetylene reduction assay is commonly used to quantify N{sub 2}-fixation and the response of N{sub 2}-fixing organisms to environmental factors. However, the technique is often criticized and conclusions based on the assay may be incorrect. In this study we compared the acetylene reduction assay to a {sup 15}N dilution method for estimating N{sub 2}-fixation in Gliricidia sepium. Seedlings were grown for 100 days under two levels of CO{sub 2} (35 and 70 Pa), air temperature (28/24 and 32/28 C day/night) and three levels of soil nitrogen (0, 1 and 10 mM). Nodule activity on a plant basis correlated well between the two methods (r{sup 2}=0.71). CO{sub 2} enrichment enhanced whole plant nodule activity by 77% and 48% as measured with the {sup 15}N dilution and acetylene methods, respectively, and 10 mM N inhibited fixation 52% and 71%. Specific nodule activity weakly correlated between the two methods (r{sup 2}=0.06). The {sup 15}N dilution method estimated a 24% increase in specific nodule activity due to increased CO{sub 2}. Acetylene assay detected a 44% suppression of specific nodule activity at l0mM N, but no effect of CO{sub 2}or temperature. Results indicate that instantaneous acetylene rate may be inaccurate when extrapolated over time. However, the integrative {sup 15}N dilution rate may miss treatment effects when interpolated to shorter time-scales. Ultimately, the choice of method depends on the hypotheses being tested. The time-scale of the phenomenon under study should approximate the time-scale of measurement.
- OSTI ID:
- 95746
- Report Number(s):
- CONF-9507129-; ISSN 0012-9623; TRN: 95:004728-0011
- Journal Information:
- Bulletin of the Ecological Society of America, Vol. 76, Issue 2; Conference: 80. anniversary of the transdisciplinary nature of ecology, Snowbird, UT (United States), 30 Jul - 3 Aug 1995; Other Information: PBD: Jun 1995
- Country of Publication:
- United States
- Language:
- English
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