Effect of arbuscular mycorrhizal fungi in roots on antioxidant enzyme activity in leaves of Robinia pseudoacacia L. seedlings under elevated CO2 and Cd exposure

Arbuscular mycorrhizal fungi (AMF) are easily influenced by increasing atmospheric CO2 concentration and heavy metals including cadmium (Cd), which can regulate antioxidant enzyme in host plants. Although the effect of AMF under individual conditions such as elevated CO2 (ECO2) and Cd on antioxidant enzyme in host plants has been reported widely, the effect of AMF under ECO2 + Cd receives little attention. In this study, a pot experiment was conducted to study the effect of AMF community in roots on superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities in leaves of 135-d Robinia pseudoacacia L. seedlings under ECO2 + Cd. The activities of SOD and CAT increased and POD activity and the richness and diversity of AMF community decreased under ECO2 + Cd relative to Cd alone. The richness and diversity of AMF were negatively related to Cd content in roots and leaves. The richness and OTUs of AMF community positively and AMF gene abundance negatively affected POD activity under the combined treatments. Superoxide dismutase and POD activities were negatively and positively related to Archaeospora and Scutellospora, respectively, under ECO2 + Cd. Cadmium in roots and leaves was negatively and significantly related to Glomus, Scutellospora, and Claroideoglomus abundance under ECO2 + Cd. Overall, AMF diversity and Archaeospora and Scutellospora in roots significantly influenced SOD, POD, and CAT activities. The response of AM symbiosis to ECO2 might regulate antioxidant capacity in host plants upon Cd exposure. Glomus, Scutellospora, and Claroideoglomus might be applied to phytoremediation of Cd-contaminated soils.