Effect of Stratification on the Dormancy of Chinese Milk Vetch Seeds (Astragalus sinicus L.)

Chinese milk vetch (Astragalus sinicus L.) is a biennial leguminous plant. Although this species is becoming a common green manure crop, Chinese milk vetch seed has a low germination rate due to low water permeability of the seed coat which is limiting factor of seeding and international seed trading. This experiment was conducted to identify a method of improving seed coat permeability. Stored seed germination rate was evaluated every 20 day from 40 days of harvest. The Chinese milk vetch seeds were stored at cold (5℃) and warm (30, 35 and 40℃) temperatures, and stratifications were treated for 20, 40 and 60 days. The data collected for seeds stored at room temperature were used as controls. In seeds stored at room temperature, dormancy was broken gradually. However, a dramatic increase of germination at 20 days after imbibition occurred 80 days after harvest, a season coincident with early September, the optimum sowing interval. Also, inhibition of germination 10 days after imbibitions occurred at 160-200 days after harvest which is consistent with a November-December interval. In the treated seed study, dry heat for 20 days induced the breaking of dormancy compared to control, however, such tendency could not be found in seeds treated for 40 days and 60 days. Cold treatment for 40 and 60 days induced dormancy. And the dormancy could be definitively broken by stratification at 30, 35 and 40℃ for 20, 40 and 60 days, with germination rates varying from 40 to 92%.