Relationship between storage period and germination of Ipomoea hederacea var. integriuscula seeds under natural condition

Morning glory (Ipomoea spp.), a problematic weed in soybean fields, is difficult to control due to its long emergence period. The intermittent germination of morning glory prolongs the emergence period, and the factors remain unclear. Therefore, we aimed to clarify the effects of different storage periods under natural conditions on germination conditions and emergence percentages of physically dormant entire-leaf morning glory (Ipomoea hederacea var. integriuscula) seeds in the field. In 2017–2020, I. hederacea var. integriuscula was cultivated in outdoor planters. Each plant was tagged on the blooming flower peduncle to record the flowering date. The seeds of I. hederacea var. integriuscula germinated 23 days after flowering (DAF). The water content of the seeds decreased rapidly until 30 DAF, and no water absorption occurred thereafter. The germination percentage of seeds in bags outdoors was low from 45 to 210 DAF, and it increased after 270 DAF irrespective of the temperature (20–35°C). On the field surface, the shorter the period of storage in bags outdoors, the lower the cumulative emergence percentage of I. hederacea var. integriuscula. The cumulative emergence was 0% in the soil for seeds of more than 90 DAF. The survival percentage of seeds in the soil increased with the number of DAFs. Therefore, the longer the DAF of the seeds, the higher the emergence of the field and survival percentage in the soil. The long period of storage on mother plants may be one of the factors associated with the long emergence period.