Drought stress substantially impacts the development and viability of Populus spp., which are essential for forestry and bioenergy production. This review summarizes and describes the functions of phytohormones, such as abscisic acid, auxins, and ethylene, in modulating physiological and molecular responses to water scarcity. Drought-induced ABA-mediated stomatal closure and root extension are essential adaptation processes. Furthermore, auxin–ABA (abscisic acid) interactions augment root flexibility, whereas ethylene regulates antioxidant defenses to alleviate oxidative stress. The advantageous function of endophytic bacteria, specifically plant growth-promoting rhizobacteria (PGPR), can augment drought resistance in spruce trees by enhancing nutrient absorption and stimulating root development. Structural adaptations encompass modifications in root architecture, including enhanced root length and density, which augment water uptake efficiency. Similarly, Arbuscular Mycorrhizal Fungi (AMF) significantly enhance stress resilience in forest trees. AMF establishes symbiotic relationships with plant roots, improving water and nutrient uptake, particularly phosphorus, during drought conditions. Furthermore, morphological alterations at the root–soil interface enhance interaction with soil moisture reserves. This review examines the complex mechanisms by which these hormones influence plant responses to water shortage, aiming to offer insights into prospective techniques for improving drought tolerance in common tree species and highlights the importance of hormone control in influencing the adaptive responses of prominent trees to drought stress, providing significant implications for research and practical applications in sustainable forestry and agriculture. These findings lay the groundwork for improving drought tolerance in Populus spp. by biotechnological means and by illuminating the complex hormonal networks that confer drought resistance.

Drought stress is a major constraint on global forestry productivity and poses a significant threat to economically important tree species such as Populus. Abscisic acid (ABA) signaling plays a central role in drought tolerance by regulating molecular, physiological, and biochemical processes. This review summarizes current knowledge of ABA signaling pathways and their roles in drought resilience in Populus. It covers physiological responses, molecular regulatory networks, hormonal crosstalk, biotechnological advances, and emerging field applications. Core ABA signaling components, including PYR/PYL/RCAR receptors, PP2Cs, SnRK2 kinases, and transcription factors such as ABFs, NACs, and MYBs, coordinate adaptive responses involved in stomatal regulation, osmotic adjustment, and root system remodeling. Integrative omics approaches, like transcriptomics, proteomics, metabolomics, and epigenomics, have provided mechanistic insights into ABA-mediated drought responses, although some regulatory mechanisms are supported by conserved evidence from model plants and require further validation in Populus. Recent biotechnological advances, including gene overexpression, RNA interference (RNAi), CRISPR/Cas9 genome editing, and emerging CRISPR-based regulatory approaches, provide new opportunities for manipulating ABA-associated drought responses in Populus. While several genome-editing and genetic approaches have been experimentally validated in Populus, many ABA-related targets remain prospective strategies requiring further functional evaluation. However, practical implementation remains limited by an incomplete understanding of hormonal crosstalk, insufficient characterization of epigenetic regulation, and ecological and social concerns. Addressing these challenges requires ecological trials, deeper analyses of hormone networks, advanced epigenetic research, robust environmental risk assessments, and interdisciplinary integration. Future progress will depend on linking molecular discoveries with physiological validation and long-term field evaluation to develop drought-resilient Populus cultivars for sustainable forestry under changing climate conditions.