## 1 Introduction  
The Karst Mountains of Southwestern China, spanning approximately 540,000 km\({}^{2}\), represent one of the most extensive continuous karst landscapes globally [1]. This region has experienced profound losses in agricultural and forestry productivity, alongside drastic declines in plant diversity, soil physicochemical characteristics, microbial diversity, and carbon sequestration capacity [2; 3; 4]. These changes are attributed to a variety of natural and human-induced disturbances, rendering it one of the areas most severely impacted by rocky desertification [5]. Vegetation plays a fundamental role in the rehabilitation of these degraded ecosystems. Prior studies have highlighted that native karst plants significantly enhance soil microbial diversity and the ability to sequester carbon [2; 3; 6]. Conversely, introduced species, such as _Pinus massoniana_ forests and _Lolium preemine_ L. grasslands, fail to positively influence soil physicochemical properties, enzymatic activity, or microbial communities [7; 8; 9; 10]. Therefore, leveraging native karst plants as primary resources and models for the transformation of rocky desertified lands, delving into the \"genetic gene pool\" of karst flora, and investigating their adaptive strategies are immensely significant endeavors. _Sophora vicifolia_ Hance, a critical leguminous shrub found across the karst mountains of Southwestern China, has gained prominence in vegetation restoration efforts within karst regions due to its exceptional drought resilience compared to other shrub species [11]. Additionally, _S. vicifolia_ serves significant economic roles, often utilized in traditional Chinese medicine [12]. Its roots have been identified as sources of various compounds, including alkaloids like matrine, which exhibit analgesic properties akin to those of pethidine, underscoring its considerable medicinal potential [12]. While the drought resistance of mature _S. vicifolia_ is well acknowledged, the challenges associated with seedling growth, particularly the constraints imposed by drought conditions on seedling development, profoundly hinder population regeneration [13; 14; 15]. Thus, examining the mechanisms through which _S. vicifolia_ adapts to drought conditions is of paramount importance. Seed germination and the seedling phase are critical junctures in a plant's life cycle, markedly susceptible to environmental conditions [16]. Abscisic acid (ABA) significantly influences plant growth within optimal concentrations [17]. ABA is pivotal in seed dormancy and germination processes, managing the synthesis of seed storage proteins, triggering and preserving seed dormancy, and overseeing germination and seedling development [18]. It also plays a crucial role in mitigating abiotic stress by regulating stomatal dynamics, dormancy, and leaf aging [19]. Research indicates that the exogenous administration of ABA can extend chlorophyll longevity in various plants, including rice, kiwifruit, and black fungus [18; 20; 21]. It elevates proline levels and protective enzyme activities, boosts cold resilience and water retention, prompts stomatal closure, diminishes transpiration rates, augments photosynthesis, and enhances leaf water content, thereby mitigating the adverse effects of drought stress [18; 20; 21]. Nonetheless, investigations into the effects of exogenous ABA on the physiological traits of woody plants, such as _S. vicifolia_, remain sparse. Present research on the drought tolerance of _S. vicifolia_ predominantly concentrates on physiological, biochemical, and transcriptomic metabolic mechanisms, alongside drought alleviation techniques like the application of exogenous calcium, arbuscular mycorrhizal fungi, microbial agents, and moisture conservers [13; 22; 23; 24]. However, an exploration into the ramifications of exogenous ABA on seed germination and the physiological responses of seedlings under drought stress is notably absent.