Global climate change has intensified land desertification in the arid and semi-arid regions of northwestern China, highlighting the urgent need to cultivate plant species with ideal architecture and well-developed root systems to combat ecosystem degradation. Amorpha fruticosa is widely used as a windbreak and sand-fixation shrub; however, its rapid growth and high transpiration during the early planting stage often result in excessive water loss, low survival rates, and limited vegetation restoration effectiveness. Plant growth retardants (PGRts) are known to suppress apical dominance and promote branching. In this study, one-year-old A. fruticosa seedlings were treated with different combinations of paclobutrazol (PP₃₃₃) and uniconazole (S₃₃₀₇) to investigate their effects on plant morphology and biomass allocation; it aims to determine the optimal formula for cultivating shrub structures with excellent windbreak and sand-fixation effects in land desertification areas. The results showed that both PP₃₃₃ and S₃₃₀₇ significantly inhibited plant height while promoting basal stem diameter, branching, and root development. Among all treatments, the S₃₃₀₇ 200 mg·L⁻¹ + PP₃₃₃ 200 mg·L⁻¹ combination (SD3) was the most effective, resulting in the greatest increases in basal diameter, branch number, total root length, and root-to-shoot ratio, while significantly reducing height increment, leaf length and leaf area (p < 0.05). Under the S₃₃₀₇ 200 mg·L⁻¹ + PP₃₃₃ 300 mg·L⁻¹ treatment (SD4), leaf width and specific leaf area were reduced by 17.92% and 38.89%, respectively, compared with the control. Correlation analysis revealed significant positive or negative relationships among most growth traits, with leaf length negatively correlated with other morphological indicators. Fresh and dry weights of both aboveground and root tissues were significantly positively correlated with basal diameter (R = 0.38) and branch basal diameter (R = 0.33). Principal component analysis demonstrated that the SD3 treatment achieved the highest comprehensive score (2.91), indicating its superiority in promoting a compact yet robust plant architecture. Overall, the SD3 treatment improved drought resistance and sand-fixation capacity of A. fruticosa by “dwarfing and strengthening plants while optimizing root–shoot allocation.” These findings provide theoretical support for large-scale cultivation and vegetation restoration in arid and semi-arid regions and offer a technical reference for growth regulation and windbreak and sand-fixation capacity in other xerophytic shrub species.

Plants growing in natural environments are constantly exposed to various biotic and abiotic stresses, among which drought is a major abiotic factor that se

Flooding, as a major abiotic stress, significantly impacts the growth and survival of poplar plantations in the floodplains of the middle and lower reaches of the Yangtze River. Elucidating the molecular mechanisms underlying flooding responses in poplar is crucial for enhancing plantation productivity. In this study, two important eastern cottonwood cultivars, Populus deltoides ‘Jianghan 1’ (HBI) and P. deltoides Bartr. CL (CL), were investigated. By integrating long-term growth surveys and transcriptome sequencing, we analyzed their phenotypic traits and molecular responses to flooding stress. After 7 years of seasonal flooding, HBI exhibited a survival rate of 73.91%, along with superior height (23.1 m) and diameter at breast height (DBH, 26.3 cm), compared with CL, indicating HBI as a flooding-tolerant cultivar. Transcriptome analysis identified 1098 shared differentially expressed genes (DEGs) in the leaves of flooded HBI and CL, which were mainly enriched in stress signal perception, oxidative stress regulation, energy metabolism and circadian rhythm. Cultivar-specific DEG analysis revealed that CL mainly activated pathways related to oxidative stress and damage repair pathways, whereas HBI-specific genes were significantly enriched in hormone signal transduction, growth regulation, flavonoid synthesis and photosynthesis. Based on this distinct enrichment pattern in the tolerant cultivar HBI, we propose that it possesses adaptive advantages under flooding stress. Specifically, HBI likely coordinates multiple physiological processes by activating ethylene and other hormone-related genes, thereby regulating hypoxia adaptation, reoxygenation-induced oxidative stress, photosynthetic recovery, and flavonoid-mediated antioxidant defense. This coordinated regulation collectively sustains growth vigor and enhances survival under seasonal inundation. Our findings demonstrate clear transcriptomic divergence underlying flooding tolerance among poplar cultivars, laying a theoretical foundation for the selection of flooding-tolerant varieties and the sustainable development of forestry in flood-prone regions. Furthermore, these results broaden the current knowledge of flooding stress biology in woody plants.

The biosynthesis and accumulation of plant secondary metabolites are tightly regulated by environmental fluctuations, serving as a crucial interface mediating plant–environment interactions. Nevertheless, the phenotypic instability of secondary metabolism-related traits induced by environmental variability has hampered the precise breeding of stress-resistant cultivars. Pinus taeda is an key timber tree species in southern China, and its foliar catechins exhibit substantial stress-resistant potential. However, phenotypic variation driven by seasonal changes has limited the germplasm innovation and genetic selection of this species. In this study, 54 half-sib families of P. taeda were used as experimental materials. Combined with near-infrared spectroscopy (NIRS) and the BLUP model, we systematically analyzed the seasonal variation characteristics, genetic parameters of catechin content (CC), and genetic gains under different breeding strategies across four seasons. Our results demonstrated that family and season had extremely significant effects on CC (p < 0.001), whereas the season × family interaction effect was not significant, indicating that the genetic expression of CC is stable across seasons. CC was higher in spring and winter but lower in summer and autumn; specifically, the mean CC in summer was 47% lower than the peak value in spring (26.95 ± 0.46 μg·g⁻¹), reflecting a resource trade-off between growth and defense metabolism. Genetic parameter analysis revealed that family-mean heritability (0.373–0.714) was higher than individual heritability and within-family heritability, with August identified as the optimal selection season. The maximum genetic gain across the three breeding strategies (individual selection, family selection, and combined selection) reached 7.86%, among which individual selection exhibited the smallest fluctuation in genetic gain. Finally, three superior families and 14 superior individuals were screened out. This study elucidates the seasonal genetic pattern of foliar CC in P. taeda, clarifies the optimal selection stage and efficient breeding strategies, and provides theoretical guidance and material support for the genetic improvement, germplasm innovation, and resource utilization of secondary metabolic traits in this ecologically and economically important tree species.