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

Abstract

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