Disruption of mycorrhizal extraradical mycelium and changes in leaf water status and soil aggregate stability in rootbox-grown trifoliate orange

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.

Mycorrhiza and Common Mycorrhizal Network Regulate the Production of Signal Substances in Trifoliate Orange (Poncirus trifoliata)

“…The soil hyphal length was determined using the protocol of Bethlenfalvay and Ames (1987). The hyphal length of nylon mesh was assayed by Zou et al (2015) in 0.05% trypan blue solution.…”

Mycorrhizal Inoculation Modulates Root Morphology and Root Phytohormone Responses in Trifoliate Orange under Drought Stress

“…Hyphal tips are hydrophilic, and thereby soil water can be taken up at the tips and transported from tips to root cortical cells, without encountering a membrane (Allen, 2007). On the other hand, mycorrhizal hyphae would extend soil water depletion zones, thus, providing mycorrhizal roots more access to available soil water (Wu et al, 2013;Zou et al, 2015). Furtherly, mycorrhizal hyphae enhance the ratio of below-ground absorptive surface to leaf area (Asrar et al, 2012).…”

“…The growth enhance by mycorrhization with F. mosseae was observed in trifoliate orange seedlings under different phosphorus substrate levels . The enhancement of growth in AM plants is often related to improvement of nutrient acquisition, especially P (Asrar et al, 2013), and direct water uptake and transport by extraradical hyphae (Abbaspour et al, 2012;Zou et al, 2015).…”

Enhancement of Drought Tolerance in Trifoliate Orange by Mycorrhiza: Changes in Root Sucrose and Proline Metabolisms

“…The underlying mechanisms of mycorrhizal plants in enhancing drought tolerance have not yet been clearly elucidated. Possible mechanisms include (i) water and nutrient uptake directly by external hyphae (Zou et al, 2015), (ii) optimizing the root system architecture (Liu et al, 2016), (iii) greater osmotic adjustment capacity (Wu et al, 2007), (iv) enhancement of antioxidant defense systems , and (v) soil structure improvement by glomalin (Wu et al, 2008).…”