## 3 Results
### Effect of Exogenous ABA on Sophora vicifolia Seed Germination under Drought Stress Induced by PEG
 } & 0\% & 30.00 \(\pm\) 8.90  & 25.63 \(\pm\) 8.98  & 25.63 \(\pm\) 1.25  & 19.38 \(\pm\) 11.25  & 30.00 \(\pm\) 16.20  \\  & 5\% & 42.50 \(\pm\) 23.18  & 29.38 \(\pm\) 7.18  & 69.38 \(\pm\) 21.25  & 51.88 \(\pm\) 15.05  & 43.75 \(\pm\) 11.27  \\  & 20\% & 3.75 \(\pm\) 3.23  & 57.50 \(\pm\) 9.13  & 43.75 \(\pm\) 12.67  & 45.63 \(\pm\) 10.08  & 25.63 \(\pm\) 29.04  \\ \hline \multirow{2}{*}{\ \begin{tabular}{c} Germination \\ potential (GP) \\ \end{tabular}  } & 0\% & 29.38 \(\pm\) 8.98  & 23.13 \(\pm\) 7.74  & 27.50 \(\pm\) 3.54  & 8.13 \(\pm\) 10.08  & 1.88 \(\pm\) 2.39  \\  & 5\% & 35.00 \(\pm\) 17.44  & 28.13 \(\pm\) 5.91  & 57.50 \(\pm\) 24.92  & 21.25 \(\pm\) 6.61  & 1.88 \(\pm\) 2.39  \\  & 20\% & 3.13 \(\pm\) 3.75  & 40.00 \(\pm\) 2.04  & 13.75 \(\pm\) 1.44  & 3.75 \(\pm\) 3.23  & 0.63 \(\pm\) 1.25  \\ \hline \multirow{2}{*}{ \begin{tabular}{c} Germination \\ Index (GI) \\ \end{tabular}  } & 0\% & 13.74 \(\pm\) 0.09  & 11.70 \(\pm\) 0.20  & 16.18 \(\pm\) 0.19  & 7.71 \(\pm\) 0.33  \\  & 5\% & 19.14 \(\pm\) 0.69  & 13.37 \(\pm\) 0.80  5: footnotemark: [ENDFOOTNOTE] & 31.34 \(\pm\) 0.50  5: footnotemark: [ENDFOOTNOTEEffect of Exogenous ABA on Malondialdehydedehyde and Proline Levels in Sophora vicifolia Seellings under Drought Stress  
Exogenous ABA and PEG had significant effects on the contents of malondialdehydedehyde (MDA) and proline (Pro) of _S. vicifolia_ (Figure 2 and Table 3). In the absence of exogenous ABA, MDA content in _S. vicifolia_ seedlings escalated with the severity of drought stress, registering significantly higher levels at both 5% and 20% PEG-induced drought stress concentrations than in CK (\(p<0.05\)). This indicates that PEG-induced drought stress prompted lipid peroxidation within the seedlings. Following the addition of ABA, there was a significant increase in MDA content across all PEG-induced drought stress treatments (\(p<0.05\)), yet no notable difference was observed among the varying ABA concentrations (\(p>0.05\)). This outcome suggests that the addition of ABA intensified the extent of lipid peroxidation in the cell membranes under drought stress, thereby leading to increased MDA production. Without ABA treatment, Pro content in _S. vicifolia_ seedlings trended upwards with increasing drought stress intensity, although this rise was not sta  
Figure 1: Effect of different concentrations of exogenous ABA on POD (**a**), SOD (**b**) and CAT (**c**) activities of _Sophora vicifolia_ under drought stress. Different uppercase letters indicate significant differences among the three PEG-6000 treatments within the same ABA treatment at \(p<0.05\) level; different lowercase letters indicate significant differences among different ABA treatments within the same PEG-6000 treatment at \(p<0.05\) level. All data are presented as mean \(\pm\) SE (standard error) (\(n=4\)). Figure 2: Effect of different concentrations of exogenous ABA on MDA (**a**) and Pro (**b**) activities of _Sophora vicifolia_ under drought stress. Different uppercase letters indicate significant differences among the three PEG-6000 treatments within the same ABA treatment at \(p<0.05\) level; different lowercase letters indicate significant differences among different ABA treatments within the same PEG-6000 treatment at \(p<0.05\) level. All data are presented as mean \(\pm\) SE (standard error) (\(n=4\)). compared to CK (\(p\) > 0.05). The addition of ABA led to a pronounced increase in Pro content, correlating with the escalation in ABA concentration (Figure 2). At a 5% PEG-induced drought stress concentration, ABA treatment at concentrations of 10 mg\(\cdot\)L\({}^{-1}\), 50 mg\(\cdot\)L\({}^{-1}\), 100 mg\(\cdot\)L\({}^{-1}\), and 200 mg\(\cdot\)L\({}^{-1}\) markedly enhanced Pro levels compared to CK (\(p\) < 0.05), with significant variation observed among these concentrations (\(p\) < 0.05).