Elevated CO2 may impair the beneficial effect of arbuscular mycorrhizal fungi on the mineral and phytochemical quality of lettuce

Abstract Arbuscular mycorrhizal fungi ( AMF ) can improve growth and nutritional quality of greenhouse‐grown lettuces cultivated at ambient CO 2 . Moreover, mycorrhizal symbiosis is predicted to be important in defining plant responses to elevated atmospheric CO 2 concentrations. Our main objective was to assess the effects of elevated CO 2 on growth and nutritional quality of greenhouse‐grown lettuces inoculated or not with AMF . Results showed that the accumulation of mineral nutrients (e.g. P, Cu, Fe) and antioxidant compounds (carotenoids, phenolics, anthocyanins, ascorbate) induced by AMF in leaves of lettuces cultivated at ambient CO 2 may diminish or disappear under elevated CO 2 . It is hypothesized that a relevant quantity of photoassimilates could be used for improving shoot growth and spreading mycorrhizal colonization in detriment to the secondary metabolism. However, important differences can be found among different cultivars of lettuces.