Populus koreana emits a wide array of volatile organic compounds (VOCs) with potential ecological functions; however, the tissue-specific distribution and underlying regulatory mechanisms of these compounds remain poorly understood. This study employed an integrated approach combining gas chromatography-mass spectrometry (GC-MS)-based metabolomics and RNA-seq to systematically profile VOC composition and gene expression in terminal buds, stems and leaves of P. koreana. A total of 207 VOCs were identified, predominantly terpenes and aromatic compounds, exhibiting distinct tissue-specific accumulation patterns. Terminal buds were enriched in limonene and caryophyllene, while leaves showed higher concentrations of alcohols and phenolic aldehydes. Transcriptomic analysis revealed 12,733 differentially expressed genes (DEGs) among the three organs, with substantial enrichment in terpenoid and phenylpropanoid biosynthetic pathways. Notably, key upregulated genes in buds, including TPS21 and PAL1, correlated with observed VOC profiles. Weighted gene co-expression network analysis (WGCNA) further identified 6365 genes strongly associated with bud-specific VOC biosynthesis. Integrated omics analyses indicated coordinated regulation of phenylalanine metabolism and transcription factors in VOC production. These findings illuminate the molecular mechanisms underlying tissue-specific VOC accumulation in P. koreana, enhancing our understanding of metabolic specialization and ecological adaptation in woody plants.

Populus simonii × P. nigra is a valuable model for studying woody plant responses to saline-alkaline stress, however the molecular mechanisms underlying its adaptation remain poorly understood. Here, integrated transcriptomic and metabolomic analyses were used to examine the responses in leaves to low (50 mmol/L) and high (200 mmol/L) alkaline salt stress over 7 and 14 days. Physiological assessments revealed that high-concentration stress inhibited growth, induced oxidative damage, elevated malondialdehyde (MDA) content, enhanced antioxidant enzyme activity (SOD, POD, CAT), and promoted osmoregulatory compound accumulation (soluble sugars, proline, free amino acids). RNA sequencing revealed extensive transcriptional reprogramming, with more pronounced changes under higher stress and longer exposure. KEGG enrichment highlighted pathways such as plant hormone signal transduction starch/sucrose metabolism, and flavonoid and phenylpropanoid biosynthesis. Metabolomic profiling detected 4257 metabolites, with notable increases in amino acids, organic acids, sugars, and flavonoids. Integrated analyses revealed coordinated regulation of genes and metabolites in phenylalanine, tyrosine, and tryptophan biosynthesis, as well as hormone signaling. Weighted gene co-expression network analysis (WGCNA) identified modules correlated with physiological traits, enriched in stress-responsive transcription factors (MYB, AP2/ERF, NAC, WRKY) and metabolic pathways. Key genes in starch/sucrose degradation, and raffinose metabolism were upregulated, whereas phenylpropanoid metabolism-related genes were suppressed. Collectively, these findings provide insight into the adaptive mechanisms of P. simonii × P. nigra to saline-alkaline stress, highlighting regulatory genes and pathways that contribute to tolerance and offering potential targets for enhancing poplar resilience in alkaline salt environments.