Funneliformis mosseae Improves Growth and Nutrient Accumulation in Wheat by Facilitating Soil Nutrient Uptake under Elevated CO2 at Daytime, Not Nighttime

The concurrent effect of elevated CO2 (eCO(2)) concentrations and arbuscular mycorrhizal fungi (AMF) on plant growth, carbon (C), nitrogen (N), phosphorus (P) and potassium (K) accumulations in plant and soil is largely unknown. To understand the mechanisms of eCO(2) and mycorrhization on wheat (Triticum aestivum) performance and soil fertility, wheat seedlings were grown under four different CO2 environments for 12 weeks, including (1) ambient CO2 (ACO(2), 410/460 ppm, daytime/nighttime), (2) sole daytime eCO(2) (DeCO(2), 550/460 ppm), (3) sole nighttime eCO(2) (NeCO2, 410/610 ppm), and (4) dual or continuous daytime/nighttime eCO(2) ((D + N)eCO(2), 550/610 ppm), and with or without AMF (Funneliformis mosseae) colonization. DeCO(2), NeCO2 and (D + N)eCO(2) generally significantly increased shoot and root biomass, plant C, N, P and K accumulation, soil invertase and urease activity, but decreased shoot and root N, P and K concentrations, and soil available N, P and K. Compared with non-AMF, AMF effects on above-mentioned characteristics were significantly positive under ACO(2), DeCO(2) and (D + N)eCO(2), but negative on plant biomass, C, N, P and K accumulation under NeCO2. Overall, AMF colonization alleviated soil nutrient constraints on plant responses to DeCO(2), while NeCO2 decreased AMF's beneficial effects on plants. These results demonstrated that an integration of AMF's benefits to plants under factual field DeCO(2) and/or NeCO2 will be critical for managing the long-term consequence of future CO2 rising on global cropping systems.