An arbuscular mycorrhizal fungus alters switchgrass growth, root architecture, and cell wall chemistry across a soil moi
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An arbuscular mycorrhizal fungus alters switchgrass growth, root architecture, and cell wall chemistry across a soil moisture gradient Binod Basyal1,2 · Sarah M. Emery2 Received: 3 June 2020 / Accepted: 7 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The abiotic environment can dictate the relative costs and benefits of plant-arbuscular mycorrhizal fungi (AMF) symbioses. While the effects of varying light or soil nutrient conditions are well studied, outcomes of plant-AMF interactions along soil moisture gradients are not fully understood. It is predicted that mycorrhizal associations may become parasitic in extreme soil moisture conditions. Under low soil moisture stress, costs of maintaining a mycorrhizal symbiont may outweigh benefits for the host plant, whereas under high soil moisture stress, the host plant may not need the symbiont. In a factorial growth chamber study, we investigated the effects of a plant-arbuscular mycorrhizal fungus symbiosis along a soil moisture gradient on growth, cell wall chemistry, and root architecture of a biofuel crop, Panicum virgatum (switchgrass). Regardless of soil moisture conditions, we found an increase in the number of tillers, number of leaves, root biomass, and amount of cellulose and hemicellulose in response to root colonization by the arbuscular mycorrhizal fungus. The fungus also increased aboveground biomass and changed several root architectural traits, but only under low soil moisture conditions, indicating a reduction in benefits of the mycorrhizal association under high soil moisture. Results from this study indicate that an arbuscular mycorrhizal fungus can increase some key measures of plant growth and cell wall chemistry regardless of soil moisture conditions but is most beneficial in low soil moisture conditions. Keywords Arbuscular mycorrhizal fungi · Drought · Soil moisture · Switchgrass · Cell wall chemistry · Root architecture
Introduction Arbuscular mycorrhizal fungi (AMF) are widespread plant symbionts, forming associations with 80% of all terrestrial plant species (Smith and Read 2010). They primarily help their host plants with nutrient and water uptake, while relying on their host for carbon (Smith and Read 2010). Under drought stress, AMF have shown positive effects on many aboveground plant growth measures such as biomass, flowering, yield, height, and tillering (Asrar et al. 2012; Marulanda et al. 2009; Secilia and Bagyaraj 1992; Wu and Xia 2006). These benefits may be because of positive effects of AMF on root growth and root architecture that help plants access water. A comprehensive meta-analysis of studies * Binod Basyal [email protected] 1
Michigan State University, 310 Plant Research Laboratory, MI, East Lansing, USA
University of Louisville, 139 Life Sciences Building, 40292, Louisville, KY 40208, USA
2
reporting AMF impacts on root/shoot (R/S) allometric partitioning demonstrated an overall increase in R/S in plants grown under a variety of abiotic stresses including drough
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