Contribution by two arbuscular mycorrhizal fungi to P uptake by cucumber (Cucumis sativus L.) from32P-labelled organic matter during mineralization in soil |
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Authors: | Erik J. Joner Iver Jakobsen |
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Affiliation: | (1) Plant Biology Section, Environmental Science and Technology Department, Risø National Laboratory, DK-4000 Roskilde, Denmark;(2) Present address: Department of Biotechnological Sciences, Agricultural University of Norway, P.O. Box 5040, N-1432, Norway |
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Abstract: | An experiment was set up to investigate the role of arbuscular mycorrhiza (AM) in utilization of P from organic matter during mineralization in soil. Cucumber (Cucumis sativus L.) inoculated with one of two AM fungi or left uninoculated were grown for 30 days in cross-shaped PVC pots. One of two horizontal compartments contained 100 g soil (quartz sand: clay loam, 1:1) with 0.5 g ground clover leaves labelled with32P. The labelled soil received microbial inoculum without AM fungi to ensure mineralization of the added organic matter. The labelling compartment was separated from a central root compartment by either 37 m or 700 m nylon mesh giving only hyphae or both roots and hyphae, respectively, access to the labelled soil. The recovery of32P from the hyphal compartment was 5.5 and 8.6% for plants colonized withGlomus sp. andG. caledonium, respectively, but only 0.6 % for the non-mycorrhizal controls. Interfungal differences were not related to root colonization or hyphal length densities, which were lowest forG. caledonium. Both fungi depleted the labelled soil of NaHCO3-extractable P and32P compared to controls. A 15–25% recovery of32P by roots was not enhanced in the presence of mycorrhizas, probably due to high root densities in the labelled soil. The experiment confirms that AM fungi differ in P uptake characteristics, and that mycorrhizal hyphae can intercept some P immobilization by other microorganisms and P-sorbing clay minerals. |
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Keywords: | arbuscular mycorrhiza external hyphae organic matter P utilization phosphorus-32 |
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