## 4 Discussion
Correspondingly, our study demonstrated that a mild drought condition (5% PEG) significantly elevated the germination rate (GR), germination potential (GP), and germination index (GI) of seeds, whereas a severe drought condition (20% PEG) substantially decreased these germination metrics. This pattern suggests that _S. vicitiglia_ is capable of adapting to drought stress by modulating its germination strategies, aligning with observations reported in prior studies [11; 14]. The ability of _S. vicitiglia_ to adjust its germination in response to varying levels of water availability highlights the plant's resilience and potential for survival and propagation in drought-prone karst environments. This finding underscores the dynamic adaptation mechanisms that _S. vicitiglia_ seedlings employ to counteract drought stress. The initial increase in peroxidase (POD) activity at a moderate drought stress level (5%) indicates an early defensive response, enhancing the scavenging of reactive oxygen species (ROS) generated due to water deficit conditions [31; 32]. As drought stress intensifies to 20%, the significant uptick in catalase (CAT) activity and malondialdehydedehyde (MDA) content reveals a heightened response to oxidative stress, indicating both enhanced antioxidant defense mechanisms and increased lipid peroxidation damage within cell membranes. This dual response mirrors the physiological adaptations observed in other plant species like _Browsonetia papyrifera_ and _Glycine max_ under similar environmental challenges [33; 34]. Therefore, the ability of _S. vicitiglia_ seedlings to modulate the activities of crucial protective enzymes such as POD and CAT under varying degrees of water scarcity is a testament to their resilience against drought-induced oxidative stress. This adjustment helps in maintaining cellular homeostasis and mitigating the deleterious effects of drought stress, albeit with the trade-off of increased lipid peroxidation as evidenced by elevated MDA levels. The findings of this study contribute valuable insights into the complex biochemical and physiological strategies employed by _S. vicitiglia_, a plant of ecological and medicinal importance, in navigating the challenges posed by drought conditions prevalent in karst environments. Impact of Exogenous Abscistic Acid on Seed Germination and Physiological Traits of Sophora vicitiglia under Drought Stress  
Extensive research highlights the pivotal role of ABA in regulating seed germination and dormancy, showing that the application of exogenous ABA can significantly bolster plant resistance to various environmental stresses [34; 35; 36]. Studies have demonstrated that soaking seeds in low concentrations of ABA markedly enhances germination rates, germination potential, and the growth of the plumule and radiicle under stress conditions, such as cold stress in _Melissitus ruthenicus_, while higher concentrations may have suppressive effects [34]. For instance, an ABA concentration of 8 mg\(\cdot\)L\({}^{-1}\) has been shown to alleviate osmotic and ionic stress in _Zea mays_ seeds caused by high soil salinity, thereby reducing damage [35]. Similarly, low-concentration ABA treatments have been reported to foster seed germination in _Oryza sativa_ under high-temperature stress, thereby boosting the plant's thermal tolerance [36]. Our study found that the germination indices (GR, GE, and GI) of _S. vicitiglia_ seeds exhibited an initial increase followed by a decrease with escalating concentrations of ABA, with the 50 mg\(\cdot\)L\({}^{-1}\) ABA treatment significantly enhancing these indices. This pattern underscores the potential of an optimal level of exogenous ABA to counteract the suppressive effects of drought stress on seed germination, suggesting that ABA plays a crucial role in augmenting plant resilience to adverse conditions, particularly drought [37].