Physical Dormancy in Seeds of Chinese Milk Vetch (Astragalus sinicus L.) from Korea

Freshly harvested seed of Chinese milk vetch (Astragalus sinicus L.; CMV) was strongly dormant because of hardseedness. Seeds of freshly harvested germinated only 8% while clipping the seed coat completely overcome the innate dormancy, which indicates inhibition of germi-nation of the seed is mainly due to seed coat (87%). The dormant (intact) hard seeds did not imbibe water whereas the non-dormant (clipped) seeds took up rapidly. In natural environment condition, the hard seed coat dormancy was broken only after 5 months after seed harvest. To break such a strong seed coat dormancy, the chemical and heat treatments were effective. Concentrated sulfuric acid was more effective than dry heat and hot water treatments. Hot water treatment improved germination but the germination percentage was less than 41%. Treatments increased germi-nation due to its effect on the seed coat integrity. A scan-ning electron microscope reveled that disruption of seed coat layers and subsequent development of numerous crack in the hilum region of the seed and on the seed coat sur-face of concentrated sulfuric acid treatment and formation of cracks in the dry heat treatments, respectively, were observed in the seed coat surface, which served as water entry points.