High Phosphorus Fertilization Increases Manganese Accumulation in Wheat: Absorption and Transport Mechanisms

Excessive intake of manganese (Mn) may cause neurological toxicity in the human body. Previous studies have shown that high phosphorus (P) fertilization can significantly increase the Mn content in wheat grain; however, the underlying mechanisms remain unclear. Here, we investigated the effects of P fertilizer application on Mn accumulation, Mn transporters, and Mn micro-distribution in wheat at varying P fertilization rates. Results indicated that high P fertilization promoted Mn accumulation in wheat at anthesis and maturity and increased Mn localization in roots and flag-leaf nodes, particularly in the enlarged and diffuse vascular bundles of flag-leaf nodes. High P fertilization upregulated the expression of Mn transporter genes TaNRAMP1 in roots and promoted the uptake of Mn by wheat, but it downregulated TaNRAMP3 expression in the flag-leaf nodes and decreased the Mn transfer factor from straw to spikes at anthesis. These findings contribute valuable insights into new strategies for mitigating the risk of high Mn levels in wheat grain and understanding the interaction between phosphorus and metal elements.