Regulation of maize root growth by local phosphorus availability, sucrose metabolism, and partitioning.

Background And Aims: Understanding how maize roots proliferate in phosphorus (P)-rich soil patches is critical for improving nutrient acquisition and crop productivity. This study explores the mechanisms of root adaptation to heterogeneous P availability, focusing on sucrose metabolism and the role of local P signals.

Methods: A split-root system with chambers of differing Pi concentrations (0 and 500 μM) was used to examine maize root responses. Various physiological and biochemical parameters, including root growth, sucrose partitioning, enzyme activities, and gene expression, were measured to elucidate the underlying mechanisms.

Key Results: Root proliferation, particularly of second-order lateral roots, was markedly enhanced in P-rich patches. Sucrose was preferentially allocated to the Pi-supplied side, as confirmed by Fourier-transform infrared (FTIR) microscopy. Sucrose content in these roots decreased, indicating active metabolism. Higher activities of cell-wall invertase and sucrose synthase were observed in the Pi-supplied roots, supporting enhanced carbohydrate utilization.

Conclusions: Local P availability triggers significant adjustments in sucrose metabolism and allocation, enhancing the sink capacity of maize roots in P-rich patches. These changes facilitate efficient lateral root proliferation and Pi utilization, highlighting the critical role of local P signals in nutrient acquisition strategies. This research provides deeper insights into the adaptive responses of maize to heterogeneous P environments, offering potential strategies for improving crop nutrient efficiency.