Effects of arbuscular mycorrhizal fungi on uptake, partitioning and use efficiency of nitrogen in wheat

Arbuscular mycorrhizal fungi (AMF) can promote the growth and yield of crops by increasing the use of nutrients. However, the influence of AMF on the uptake, utilization and partitioning of nitrogen (N) from different sources remain uncertain. Therefore, we investigated AMF inoculation on plant biomass, N-uptake (from fertilizers and soil), -partitioning and N use-efficiency (NUE) in two wheat cultivars using 15N isotope labeling in a field and pot experiment. Results showed that AMF inoculation increased both plant biomass and N accumulation, and altered N partitioning in wheat. AMF inoculation significantly increased root N concentration and decreased grain N concentration (GNC) and leaf N concentration. The decrease in GNC by the AMF was mainly attributed to the variations in pre-anthesis accumulated N in vegetative organs and a reduction in the amount of N translocation. AMF significantly increased root dry weight by 13.5-18.2%, N uptake of the root by 25.4-37.2%. The N partitioning ratio in roots increased, but decreased in grains. Further, AMF significantly increased plant uptake of top-dressed 15N-labeled fertilizer by 15.0-17.8%. AMF promoted grain N absorbed from fertilizer (basal and topdressing fertilizer) but reduced its uptake from soil. Importantly, fertilizer N recovery efficiency (FNRE), N utilization efficiency (NUtE) and NUE were higher in AMF than in the control (CK), demonstrating the benefits of AMF inoculation on growth in wheat. Therefore, using AMF as biofertilizers in field conditions may be an effective agronomic practice in order to ensure sustainable production.