Germination of Wasabia japonica Matsum. Seeds

Abstract

Germination of Wasabia japonia Matsum. seeds, typical recalcitrant crop seeds in Japan, was investigated. Wasabia seeds have deep dormancy, but during storage the dormancy weakens. In eight months after harvest, the dormancy almost all disappears, resulting in the heavy sprouting of stored seeds. Optimum germination temperature is 15-degrees-C. In deep dormant period, 20-degrees-C or higher temperature cannot induce full germination. At 10-degrees-C, germination speed is very slow, though the similar germination percentage can be attained as in 15-degrees-C. GA4 is more effective than GA3 in breaking the dormancy. Germination percentage is higher and mean germinating days is smaller in GA4 than in GA3. BA and thiourea are effective to some extent for dormancy breaking. Combination of GA3 and BA shows about as the same effectiveness as GA4. Decoated seeds show almost perfect germination even in the deep dormant period, showing the cause of dormancy is mainly due to seedcoat.