Effects of Exogenous Phosphorus and Hydrogen Peroxide on Wheat Root Architecture

Plant root growth and architectural modifications are well-documented responses to phosphorous (P) starvation. The spatiotemporal dynamics of hydrogen peroxide (H₂O₂) in mediating root development under P deficiency, especially in cereal crops like wheat, remain insufficiently understood. A nutrient solution experiment was conducted to grow two varieties of wheat, including SM15 and HG35, with the treatments of 0.005 and 0.25 mmol/L P supply. Exogenous H₂O₂ and its scavenger ascorbic acid (AsA), and a NADPH oxidase inhibitor diphenylene iodonium (DPI) were added. The distribution of reactive oxygen species (ROS) in roots were detected by chemical staining and fluorescent probe technology. Low P supply did not change the root dry weight and total root length, while it decreased the lateral root density. The increase in the primary root and lateral root growth in P-starved wheat coincided with more ROS in the cell wall of the elongation zone. ROS production and oxidative enzyme activity of P-starved roots increased significantly. Low H₂O₂ induced the formation of lateral roots and significantly increased lateral root density under low P conditions. High H₂O₂ significantly reduced lateral root density but stimulated the nodal root formation. Exogenous AsA or DPI addition reversed the promotion of root growth imposed under the low P treatment or H₂O₂ addition. Furthermore, exogenous H₂O₂ treatment reduced the inhibitory effect of the DPI treatment on nodal root formation. It is suggested that the involvement of ROS in the regulation of wheat root system architecture under low P supply.