Influence of arbuscular mycorrhizal fungi on low molecular weight soluble compounds in the rhizosphere soil of black locust seedlings grown in cadmium-contaminated soils under elevated CO2 scenarios

AimsLow molecular weight soluble compounds in rhizosphere soils are important composition of soil organic carbon, which are mainly derived from root exudates and easily affected by biological and abiotic factors. Here, we investigated the effect of arbuscular mycorrhizal fungi (AMF, Funneliformis mosseae) on soluble sugars, flavonoids, and phenolic acids in the rhizosphere soil of black locust seedlings grown under elevated CO2 and Cd-contaminated soils.ResultsF. mosseae decreased (p < 0.05) contents of mannose, glucose, galactose, arabinose, total flavonoids, quercetin, total phenolic acids, gallic acid, chlorogenic acid, p-hydroxybenzoic acid, and caffeic acid in rhizosphere soils under elevated CO2 + Cd; however, the concentration of p-coumaric acid increased (p < 0.05). Additionally, F. mosseae led to significant decreases in mannose, galactose, quercetin, gallic acid, chlorogenic acid, and p-hydroxybenzoic acid in roots under elevated CO2 + Cd; however, glucose content in roots increased (p < 0.05). Contents of small compounds in roots significantly affected low molecular weight soluble compounds in rhizosphere soils, and F. mosseae colonization rate and rhizosphere soil C, pH, and DTPA-Cd significantly influenced the accumulation of low molecular weight soluble compounds.ConclusionsF. mosseae colonization significantly decreased the accumulation of low molecular weight soluble compounds in the rhizosphere of black locust under elevated CO2 + Cd, leading to significant increases in pH and Cd content in rhizosphere soils, which could improve our understanding of the regulation of AMF on rhizosphere soil carbon pool and the migration of heavy metals under elevated CO2 scenarios.

Automated summary

This study investigated the effect of arbuscular mycorrhizal fungi (AMF) on soluble sugars, flavonoids, and phenolic acids in the rhizosphere soil of black locust seedlings. The results showed that AMF significantly decreased the accumulation of low molecular weight soluble compounds in the rhizosphere soil and led to an increase in pH and Cd content. These findings contribute to our understanding of the regulation of AMF on rhizosphere soil carbon pool and the migration of heavy metals under elevated CO2 scenarios.