Abstract
As a fundamental investigation of controlling Alopecurus aequalis, a noxious weed in wheat and barley cultivation on drained paddy fields, the primary dormancy of the seed was studied. The results are as follows: 1. The glumes have no part in the dormancy, and the seed coat does not inhibit the seed itself from absorbing water. 2. The period of dormancy varies according to the moisture content of the seed during its storage. In case of high moisture content of seeds, such as a wet storage at 20°C (with about 55% moisture content of seeds) or a dry storage in a paper bag at room temperature (about 15% moirture), the dormancy lasts about 4 months after harvest, while it lasts longer when seeds are stored in a desiccator at room temperature (6%) 3. Low-temperture treatment is effective to overcome the dormancy in wet condition at temperature ranging from 1°C to 5°C (Fig. 1). Drying the seeds or placing them in a moist condition at 30°C for one day or more after the treatment lowers the effect of overcoming the dormancy. A low-temperature treatment in absenoe of oxygen is less effective (Fig. 2). 4. Placing the seeds at temperatures higher than the germination temperture (high-temperature tretment) is also effective to overcome the dormancy unless the seeds lose their vitality. This treatment is most effective in moist conditions at 30°C (Fig. 3), and effective in the same manner for the seeds buried in the soil. The treatment in absence of oxygen is much more effective (Fig. 4). 5. 5°C/20°C alternating-temperature treatment accelerates the effect of low-temperature treatment (Fig. 5A). 10°C/12°C alternating-temperature treatment is also effective to overcome the dormancy (Fig. 5B). 6. The dormant seeds germinate slowly if the seed coats are pricked with a pin (Fig. 6). The pricked seeds can not germinate if the pricked openings are covered with paraffin (Fig. 7). 7. As the results of these findings, it was clarified that high temperature in the absence of oxygen under submerged soil in summer is important for overcoming the dormancy of the seeds in paddy fields.
