A Newly-Discovered Benefit of Mycorrhizal Fungi
Rinaudo, V., Barberi, P., Giovannetti, M. and van der Heijden, M.G.A. 2010. Mycorrhizal fungi suppress aggressive agricultural weeds. Plant and Soil 333: 7-20.
Rinaudo et al., as they describe it, "investigated the impact of AMF and AMF diversity (three versus one AMF taxon) on weed growth in experimental microcosms where a crop (sunflower) was grown together with six widespread weed species."
In the words of the four researchers, "the total biomass of sunflower grown alone in monocultures was 22% higher compared to microcosms where sunflower was grown in mixture together with weeds," while "the total weed biomass in microcosms with sunflower was on average 47% lower in microcosms with AMF, compared to microcosms without AMF." And when the weeds were grown alone, the effect of AMF presence was to reduce weed biomass by 25%.
Rinaudo et al. say their study shows that "AMF have the ability to suppress growth of some aggressive agricultural weeds, including Chenopodium album and Echinocloa crus-galli, which belong to the top ten of the world's most aggressive weeds." In addition, they note that the sunflower plants they grew "benefited from AMF through improved phosphorus uptake," which "points to a novel characteristic of the mycorrhizal symbiosis, namely that AMF have the ability to suppress unwanted weed species, while at the same time promoting nutrition of the target crop species," which work "supports two earlier reports by Vatovec et al. (2005) and Jordan and Huerd (2008)." And in further commenting on this aspect of their work, they say that "sunflower obtained 48% more phosphorus when AMF were present, while AMF reduced weed phosphorus content of the three mycorrhizal weeds (Digitaria sanguinalis, Echinochloa crus-galli, Setaria viridis) by 21%."
The significance of these findings with respect to the ongoing rise in the air's CO2 content is linked to the relationship that exists between atmospheric CO2 enrichment and AMF growth and development. As the air's CO2 content rises, it will likely impact crop-fungal interactions by increasing the percent of the crop's root system colonized by either mycorrhizal fungal hyphae or arbuscular structures, thereby promoting the positive phenomena documented by Rinaudo et al.
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