Abstract: 【Objective】To investigate the effects of the sterol derivative SC303 on seed germination and seedling root morphology of soybean,and provide a reference for soybean production.【Methods】Five concentrations of SC303 were established：0.02 μmol/L（T1）,0.10 μmol/L（T2）,0.50 μmol/L（T3）,2.50 μmol/L（T4）,and 5.00 μmol/L（T5）,with distilled water as the control（CK）. Soybean variety Heihe 43 was soaked for 8 h. On days 1,3,5,and 7 of the germination test,amylase activities in cotyledons,cotyledons and root free amino acids content of soybean were measured. Germination rate,germination potential and root morphological indicators were analyzed,and the correlations among these indicators were evaluated via Mantel test.【Results】Seed soaking with different concentrations of SC303 significantly affected soybean seed germination and the germination rates of T1,T4 and T5 treatments were 96.00%,92.00% and 95.33%,respectively,all significantly higher than that of CK（P<0.05）;the germination potential of T1 treatment was the highest（92.00%）,which was significantly higher than that of CK（P<0.05）. The amylase activity in soybean cotyledons of each treatment was significantly different and the effect of T3 treatment performed best,with amylase activity of 0.55 U/g on day 1,reaching a peak on day 5（0.76 U/g）,and maintaining a high level on day 7（0.70 U/g）,all significantly higher than that of CK（P<0.05）;the content of free amino acids in cotyledons of T3 treatment was 348.19 mg/g on day 5,which was significantly increased by 93.60% compared with CK（P<0.05）,and was 328.20 mg/g on day 7. The contents of free amino acids in root of T3 and T4 treatments on day 1 were 83.04 and 86.86 mg/g,respectively,which were significantly higher than that of CK（P<0.05）. The total root length,root volume,root surface area and root tip number of T3 treatment were the highest,reaching 96.62 cm,0.35 cm³,21.53 cm² and 167.50,respectively. Mantel analysis indicated that germination characteristics were extremely significantly positively correlated with the amylase activities in cotyledons on days 1,3,and 5（Mantel′s r>0.4,P<0.01）,and with the content of free amino acids in root on day 5（Mantel′s r>0.4,P<0.01）;root morphological characteristics were extremely significantly positively correlated with the contents of free amino acids in root on days 3 and 5（Mantel′s r>0.4,P<0.01）.【Conclusion】The treatment with 0.50 μmol/L SC303 significantly increases the amylase activity in soybean cotyledons and the content of free amino acids in root,providing material support for seed germination. It also promotes root elongation,expands root surface area,increases the number of root tips,and optimizes root architecture. This concentration is suitable for promoting soybean seed germination and early root establishment,showing development potential.

Key words: Soybean, SC303, Sterol derivative, Seed germination, Root morphology