Arbuscular mycorrhizal fungi (AMF) can improve growth and nutritional quality of greenhouse-grown lettuces cultivated at ambient CO2. Moreover, mycorrhizal symbiosis is predicted to be important in defining plant responses to elevated atmospheric CO2 concentrations. Our main objective was to assess the effects of elevated CO2 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 CO2 may diminish or disappear under elevated CO2. 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.
