Abstract

Nitrogen (N) and abscisic acid (ABA) are important nutrients and signaling molecules in regulating plant growth and stress responses. Although the crosstalk between ABA and N has been widely noted, our understanding of the process and mechanism underlying their interaction remains limited. Here, we found that exogenous ABA influenced the growth and N utilization efficiency (NUE) of Populus cathayana depending on N supply level. Integrated transcriptome analysis identified a substantial number of overlapping differentially expressed genes in the leaves following both exogenous ABA treatment and N deficiency, indicating potential crosstalk between ABA and N signaling pathways. Cross‐treatment experiments demonstrated that ABA significantly enhanced biomass accumulation and NUE in poplar under N‐deficient and N‐excessive conditions. Elemental analysis further revealed that ABA significantly altered N distribution among leaves. Additionally, asparagine synthetase (EC 6.3.5.4), a key enzyme in N assimilation, was significantly induced by both ABA and N availability, contributing to N distribution and influencing aboveground growth in P. cathayana. Furthermore, genes associated with N metabolism and transport, such as PcASN1, PcNRT2.5, PcNRT3.1, PcNPF4.1 and PcGDC1, were found to be co‐regulated by N and ABA. Therefore, these results reveal a mechanism by which ABA enhances N utilization, pointing to a new strategy for optimizing poplar NUE.