The Impact of Nitrogen and Phosphorus Interaction on Growth, Nutrient Absorption, and Signal Regulation in Woody Plants

This article methodically reveals how, in woody plants (poplar), the interaction between N and P coordinates root structure and nutrient absorption through a complex hormone signaling network. This study bridges a significant gap in our knowledge of nutrient interaction networks. The results demonstrate that NO3− significantly enhances the gene expression and enzymatic activity of organic acid synthases (MDH, PEPC) and APs. Furthermore, it synergizes with IAA/ABA signals to refine root structure, enhancing the surface area for P absorption. In low Pi availability environments, NO3− further promotes P recycling by simultaneously boosting the levels of Pi transport proteins (notably, the PHO family), facilitating myo-inositol phosphate metabolism (via IMP3/ITPK1-mediated PP-InsPs degradation), and augmenting IAA/SA signals. Pi induces the activity of N assimilation enzymes (GS/GOGAT/GDH), facilitating nitrogen metabolism. However, in the absence of N, it leads to a metabolic imbalance characterized by high enzymatic activity but low efficiency. Alternatively, adequate N availability allows Pi to improve root robustness and N assimilation efficiency, mediated by IAA/GA accumulation and ABA signaling (e.g., SNRK2/ABF). We propose the existence of an intricate network in poplar, orchestrated by transcriptional cascades, metabolic regulation, and hormonal synergism. Key modules such as SPX-PHR, NLA, HHO2, and MYB59 are likely central to this network’s function. These findings offer a foundational framework for the development of molecular breeding and precise fertilization strategies, enhancing the efficient use of N and P in forestry.