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Research article - Peer-reviewed, 2006

Phosphorus, nitrogen and their interactions affect N-2 fixation, N isotope fractionation and N partitioning in Hippophae rhamnoides

Gentili, F


The interactive effects of varying phosphorus and nitrogen supplies on N-2 fixation, N isotope fractionation during N uptake, and N partitioning among plant parts were studied in the actinorhizal plant Hippophae rhamnoides L. (sea buckthorn). Plants were grown for six weeks after inoculation with the N-2-fixing actinomycete Frankia and differences in N accumulation were used to quantify N-2 fixation. N-15 natural abundance was analysed to study N isotope fractionation in specific plant parts in plants receiving different levels of N and P. Furthermore, the root system was split to study N isotope fractionation in roots supplied with different levels of N and P. Phosphorus stimulated N-2 fixation by direct effects on nodule dry matter and nodule function, rather than indirectly via plant growth. Phosphorus also stimulated N uptake from solution and influenced N isotope fractionation during N uptake. The inclusion of N-15 natural abundance analyses made it possible to detect P effects on N uptake, fractionation and N-2 fixation even though the plants used both N-2 fixation and combined N as N sources


Hippophae rhamnoides; isotope fractionation; nitrogen; 15N; N2 fixation; phosphorus

Published in

2006, volume: 41, number: 1, pages: 39-45

Authors' information

UKÄ Subject classification

Landscape Architecture
Agricultural Science
Food Science

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