Abstract
Arbuscular mycorrhizas possess well developed extraradical mycelium (ERM) network that enlarge the surrounding soil for better acquisition of water and nutrients, besides soil aggregation. Distinction in ERM functioning was studied under a rootbox system, which consisted of root+hyphae and root-free hyphae compartments separated by 37-μm nylon mesh with an air gap. Trifoliate orange (Poncirus trifoliata) seedlings were inoculated with Funneliformis mosseae in root+hyphae compartment, and the ERM network was established between the two compartments. The ERM network of air gap was disrupted before 8 h of the harvest (one time disruption) or multiple disruptions during seedlings acclimation. Our results showed that mycorrhizal inoculation induced a significant increase in growth (plant height, stem diameter, and leaf, stem, and root biomass) and physiological characters (leaf relative water content, leaf water potential, and transpiration rate), irrespective of ERM status. Easily-extractable glomalin-related soil protein (EE-GRSP) and total GRSP (T-GRSP) concentration and mean weight diameter (MWD, an indicator of soil aggregate stability) were significantly higher in mycorrhizosphere of root+hyphae and root-free hyphae compartments than non-mycorrhizosphere. One time disruption of ERM network did not influence plant growth and soil properties but only notably decreased leaf water. Periodical disruption of ERM network at weekly interval markedly inhibited the mycorrhizal roles on plant growth, leaf water, GRSP production, and MWD in root+hyphae and hyphae chambers. EE-GRSP was the most responsive GRSP fraction to changes in leaf water and MWD under root+hyphae and hyphae conditions. It suggests that effect of peridical disruption of ERM network was more impactful than one-time disruption of ERM network with regard to leaf water, plant growth, and aggregate stability responses, thereby, implying ERM network aided in developing the host plant metabolically more active.
Highlights
Plant rhizosphere often inhabits a kind of beneficial soil fungi from the phylum Glomeromycota known as arbuscular mycorrhizal fungi (AMF), which can colonize the roots of ∼80% land’s plants to form arbuscular mycorrhizas (AMs) (Smith and Read, 2008)
Root mycorrhizal colonization was not significantly different when compared between extraradical mycelium (ERM)-O and ERM treatments
This could lead to an AMF inoculum less effective, strongly decreasing the root AM colonization
Summary
Plant rhizosphere often inhabits a kind of beneficial soil fungi from the phylum Glomeromycota known as arbuscular mycorrhizal fungi (AMF), which can colonize the roots of ∼80% land’s plants to form arbuscular mycorrhizas (AMs) (Smith and Read, 2008). Extraradical mycelium (ERM) network in the soil, a key component of AMs, extends far beyond the root zone to acquire labile forms of soil mineral nutrients and water for the host plant (Selosse et al, 2006) and many infochemicals from one plant to another (Simard and Durall, 2004; Achatz and Rillig, 2014). ERM has been reported to facilitate the free exchange of nutrients and water within the fungal mycelium (Barto et al, 2012). No such evidence showing the role of ERM on water absorption is available. The ERM contribution of water transfer to host plant is only a small percentage (EgertonWarburton et al, 2007). Khalvati et al (2005) found that as low as 4% of water in hyphal compartment was transferred to the root compartment by ERM
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