Phosphorus acquisition from phytate depends on efficient bacterial grazing, irrespective of the mycorrhizal status of Pinus pinaster

Abstract

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Ecological importance of soil bacterivores for ecosystem functions

“…This negative effect of mycorrhizal fungi on ES m was very low for shoot biomass (−5 %) but substantial for root biomass (−104 %), showing that even when mycorrhizal fungi reduced the positive effect of bacterivores on root growth, the positive effects of bacterivores on plant nutrition were still maintained. The few existing studies support this hypothesis for both plants infected by arbuscular (Koller et al 2013b;Koller et al 2013c) and ectomycorrhizal fungi (Bonkowski et al 2001b;Irshad et al 2012). These results also support the hypothesis formulated by Bonkowski et al (2001b) assuming that the mycorrhizal and the bacteriabacterivore mutualisms complement each other and plant resources are allocated to optimize simultaneous exploitation of both mutualistic relationships.…”

“…However, this positive effect was greatly variable among studies (Table 1). Shifts in root architecture were also observed for bacterial-feeding nematodes but to a lesser extent than for protists (Cheng et al 2011;Irshad et al 2012;Irshad et al 2011). For instance, while protists increased the number of root tips on average by a factor of 2.5, nematodes only increased the number of tips by a factor of 1.2 (Table 1).…”

“…Using P radio-isotopes is probably the best way to better understand how bacterivores affect P cycling at the soil-plant interface. Also, the literature indicates that a large number of other ecological factors are likely to impact bacterivore-effects on ecosystem functions: bacterivore species (Cheng et al 2011;Ferris et al 1997), soil properties (Ekelund and Rønn 1994), plant species, or cultivars (Somasundaram et al 2008), the presence of symbiotic mutualists (Herdler et al 2008;Irshad et al 2012) or other free fauna (Bonkowski and Schaefer 1997;Tao et al 2009), time after inoculation (Krome et al 2009a), etc. Unfortunately, the number of observations for each factor was too low or difficult to aggregate to perform a metaanalysis.…”

Advances and Perspectives to Improve the Phosphorus Availability in Cropping Systems for Agroecological Phosphorus Management

“…In wheat, cultivars shape distinctive communities in conventional agroecosystems and cultivareAMF interactions show complex patterns (Mao et al, 2014). Additionally, grazing of bacteria by nematodes, amoeba, or collembolans is an active process for better utilization of poorly accessible organic P (Irshad et al, 2012).…”

Rhizosphere 3: where plants meet soils down-under

“…This is emphasised by two papers in this Special Issue. Irshad et al (2012) show that poorly available organic P could be made available to plants only through the grazing by nematodes of phytaseproducing bacteria, and Jin et al (2012) report that elevated CO 2 may increase the amount of P immobilised by microorganisms in the rhizosphere. These complex interactions are likely to be the focus of much future research.…”