Mycorrhiza and common mycorrhizal network regulate the production of signal substances in trifoliate orange (Poncirus trifoliata)

Abstract

Common mycorrhizal networks (CMNs) connecting two or more neighbouring plants are confirmed to transfer signals, whereas little information about CMNs effects on the signal substances production is known. In this study, a two-chambered rootbox separated by 37 μm nylon mesh was used to establish donor and receptor chambers. Two chambers both were planted with trifoliate orange (Poncirus trifoliata) and then only donor chamber inoculated with Diversispora versiformis, Paraglomus occultum and Rhizoglomus intraradices. The roots of the donor and receptor plants both were mycorrhizated suggesting that CMNs were established between donor and receptor seedlings. Moreover, the AMF association dramatically increased plant height, stem diameter, leaf numbers, and shoot and root biomass in both the donor and receptor seedlings. The AMF inoculation in the donor plants and the subsequent mycorrhizal colonization by CMNs in the receptor plants significantly increased root calmodulin (CaM) and salicylic acid (SA) concentrations, while considerably decreased root nitric oxide (NO) and jasmonic acid (JA) concentrations. This was accompanied by down-regulated expression of three JA synthetic genes (PtLOX, PtAOS and PtAOC), regardless of donor and receptor seedlings. These results thus suggest that CMNs between trifoliate orange seedlings manifestly promote plant growth and affect the production of signal substances.