Effects of arbuscular mycorrhizal fungi on maize nitrogen uptake strategy under different soil water conditions

Aims Arbuscular mycorrhizal fungi (AMF) could influence plant abilities of total nitrogen (N) acquisition. Global changes have been influencing availabilities of different N forms and water resources in soil. However, it is uncertain whether and how AMF colonization affects plant uptake and preference of different N forms and how are they affected by soil water conditions. Methods We conducted a pot experiment with Funneliformis mosseae (a common arbuscular mycorrhizal fungal species) colonized and non-colonized maize (Zea mays L.) growing at low and high water conditions, the growth medium contained much more nitrate (NO3-) than ammonium (NH4+). Results F. mosseae colonization and high water availability increased maize biomass and total N uptake. Enhanced water supply increased proportional contributions of NH4+ to colonized and non-colonized maize because high water conditions may increase NH4+ accessibility to maize. F. mosseae colonization weakened proportional contributions and preference of NH4+ in maize, indicating that AMF enable plants to prefer using the more abundant N form and develop more beneficial N uptake strategies considering that NO3- was more dominant than NH4+ in growth medium. Furthermore, maize NH4+ preference was decreased by F. mosseae colonization more under high than low water conditions. This demonstrated greater effects of AMF on regulating plant N uptake strategies in soils with greater water availability. Conclusions This work revealed the regulation of AMF colonization on plant N uptake strategies under different soil water conditions. The findings enriched our knowledge of plant N use in the context of global changes.