Keywords: 
• botany /
• Hydrocotyle vulgaris /
• aquatic extract /
• allelopathy /
• seed germination

Abstract: To understand the allelopathic potential of Hydrocotyle vulgaris and to determine the effect of the aquatic extract from its leaves and roots on seed germination and seedling growth，three plant types：radish （Raphanus sativus），cucumber （Cucumis sativus），and Chinese cabbage （Brassica chinensis） were studied using 50.0 gL-1 leaf extract and root extract. A correlation analysis was utilized. Results showed that the aquatic root and leaf extract for high density H. vulgaris had strong （P＜0.01） allelopathic effects on seed germination with the seed germination rate positively correlated to the density of the extract，with a treatment of 50.0 gL－1 of the aquatic root extract seed germination was reduced 29.3% for radish，14.6% for Chinese cabbage，and 41.4% for cucumber，and reduced 51.1% for radish，39.0% for Chinese cabbage，and 100% for cucumber of the aquatic leaf extract. After germination，continue to treat with 50.0 gL－1 of the aquatic root extract and leaf extract to test the growth of radicals and buds. Result shows that with the treatment of root extract，the fresh weight of radicals was reduced 22.1% for radish，46.2% for Chinese cabbage，and 34.3% for cucumber，and the fresh weight of buds was reduced 58.1% for radish，50.2% for Chinese cabbage，and 58.9% for cucumber. The leaf extract had higher inhibition rate than root on fresh weight. Thus，the aquatic leaf extract had stronger allelopathic effects than roots.［Ch，3 tab. 15 ref.］