1976 Volume 21 Issue 2 Pages 56-60
Seeds of common lambsquarters (Chenopodium album L.), Himeinubie, a variety of barnyardgrass (Echinochloa crusgalli Beauv. var. praticola Ohwi), and pale smartweed (Polygonum lapathifolium L.) were buried in soil in Wagner pots and held in incubators at 5° or 10°C. After 70-80 days, the seeds were recovered in the dark and examined for their response to temperature conditions. Prior to incubation, a half of the seeds were preirradiated by sunlight for 5 minutes, and the other half of the seeds were kept in the dark. The temperature conditions included 21 treatments: at the constant temperatures of 5°, 10°, 15°, 20°, 25°, and 30°C, and 15 combinations of alternating temperature.
The seeds kept in darkness showed a higher germination percentage at the alternating temperatures. In common lambsquarters, marked effects were given by a temperature shift greater than 15°C from the lower temperature of 5°C. At a lower range of temperature of 5° and 10°C followed by a higher range of temperature below than 20°C, the seeds of Himeinubie failed to germinate, but were successful when followed by 25°C. At 30°C, however, germination proceeded considerably without any temperature alternation. In pale smartweed, the reaction of seeds to the temperature was similar to common lambsquarters at 15° and 20°C, and to Himeinubie at 25° and 30°C respectively. The seeds preirradiated showed a great promotion in germination at the wide range of temperature conditions.
It was proved that the seasonal germination curves estimated from both the germination percentage in laboratory and the temperature of soil surface, almost coincided with the observed seasonal changes in emergence in the field in the case of common lambsquarters and Himeinubie during the period from spring to summer. It was probable, however, that an induced dormancy was involved in emergence of pale smartweed during the period from summer to autumn and common lambsquarters in autumn.
