Abstract: Taking alfalfa (Medicago sativa L. ‘XinMu No.4’) as a test object,the plant growth regulator GA₃ (gibberellin) was sprayed at different growth stages of alfalfa to investigate how the GA₃ affect endogenous hormone content in flower and pod,seed yield components and pod setting rate. The results showed that:in the budding stage,the endogenous hormones GA₃ and ZR(zeatin riboside) contained in flower and pod were decreased significantly (P<0.05) after 100 mg·L^-1 GA₃ was sprayed on the leaf surface of alfalfa,but it has little effect on the content of ABA(abscisic acid) and IAA(auxin). In the early flowering stage,the endogenous hormones GA₃ and IAA contained in flower and pod increased significantly(P<0.05) under the same experimental treatment,but the content of ABA and ZR were not the case. In the full flowering stage,the content of IAA decreased significantly(P<0.05) but GA₃,ABA,ZR did not. In the podding stage,the content of IAA and ZR decreased significantly(P<0.05) but GA₃ and ABA did not. The comprehensive analysis of grey correlation degree between yield components and seed yield indicated that the comprehensive score of full flowering stage treatment was the highest,and the thousandseed weight and pod setting rate were the main factors affecting seed yield. The treatment of spraying 100 mg/L GA₃ on leaves had little influence on alfalfa yield components. However,Spraying in the budding stage had a greater effect onseed yield,which was 48.24% lower than that of the control group. In conclusion,the suitable period for GA₃ spraying is the fullbloom stage,and low concentration spraying is recommended in alfalfa seed production.

Key words: Alfalfa, GA₃, Endogenous hormone, Yield component factors

摘要： 本试验以‘新牧4号’紫花苜蓿（Medicago sativa L.‘XinMu No.4’）为试验材料，在不同生育时期喷施植物生长调节剂赤霉素（gibberellin，GA₃），探讨紫花苜蓿花荚内源激素含量变化及其对种子产量构成和结荚率的影响。结果显示：在现蕾期苜蓿叶面喷施100 mg·L^-1 GA₃后，可显著降低花荚内源激素GA₃和玉米素核苷（zeatin riboside，ZR）含量（P<0.05），对脱落酸（abscisic acid，ABA）和生长素（auxin，IAA）含量影响较小；初花期喷施可使花荚内源激素GA₃和IAA含量显著增加（P<0.05），对ABA与ZR含量影响较小；盛花期喷施可导致花荚内源激素IAA含量显著降低（P<0.05），但对GA₃，ABA和ZR含量影响较小；结荚期喷施则引起花荚内源激素IAA和ZR含量显著性下降（P<0.05），而对GA₃和ABA含量影响较小。产量构成因子与种子产量灰色关联度综合分析表明，盛花期处理综合得分最高，种子千粒重和结荚率是影响苜蓿种子产量的主要因素；喷施100 mg·L^-1 GA₃处理对紫花苜蓿产量构成因子影响不大，但现蕾期喷施对种子产量影响较大，较对照组降低48.24%。综上所述，喷施GA₃的适宜时期为盛花期，在苜蓿制种生产中建议使用低浓度喷施。

关键词: 紫花苜蓿, GA₃, 内源激素, 产量构成因子