Arbuscular mycorrhizae affect the N and C economy of nodulated Phaseolus vulgaris ( L.) during NH 4 + nutrition

• Published in: Soil biology & biochemistry Vol. 41; no. 10; pp. 2115 - 2121
• Main Authors: Mortimer, P.E., Pérez-Fernández, M.A., Valentine, A.J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 2009; Elsevier
• Subjects: Agronomy. Soil science and plant productions; Arbuscular mycorrhiza; Biochemistry and biology; Biological and medical sciences; C economy; Chemical, physicochemical, biochemical and biological properties; Economic plant physiology; Fundamental and applied biological sciences. Psychology; N metabolism; NH 4; Nodules; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); N metabolism; C economy; NH 4; Arbuscular mycorrhiza; Nodules; Ammonium; Nutrition; Nodulation; Plant nodule; Metabolism; Symbiont; Grain legume; Economy; Endomycorrhiza; Leguminosae; Vegetable crop; Phaseolus vulgaris; Dicotyledones; Angiospermae; Mycorrhiza; Spermatophyta; Soil science; NH
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2009.07.021

In the symbiosis between nodulated legume roots and arbuscular mycorrhizal (AM) fungi, the C and N economy can be influenced by the source of N-supply from either AM-derived NH 4 + uptake or nodule-derived biological nitrogen fixation (BNF). This relationship was investigated in terms of NH 4 + supply and BNF by the two symbionts. Nodulated Phaseolus vulgaris seedlings with and without AM, were hydroponically grown with either 0 N or 1 mM NH 4 + supply. Plants were harvested at 30 days after emergence and measurements were taken for biomass, N 2 fixation, photosynthesis, CO 2 and O 2 root respiration, calculated C and N economy. AM roots had higher NH 4 + uptake and this was associated with the suppression of BNF and nodule growth. The higher NH 4 + uptake in AM roots occurred with lower root maintenance respiration, compared to when N was derived from BNF. There was also an increase in the below-ground sink strength of NH 4 + fed AM roots compared to NH 4 + fed non-AM roots, as evidenced by the increases in root CO 2 and O 2 respiration and photosynthetic stimulation. These results indicate that although the AM root had higher total below-ground respiratory costs during NH 4 + nutrition, there were lower respiratory C costs associated with N derived from AM symbionts in comparison to N from BNF.