北海道における一年生畑雑草の発生生態に関する研究
スポンサーリンク
概要
- 論文の詳細を見る
The experiments reported here are the summary of the results carried out to clarify seed behaviour in the field in relation to emergence of three representative weeds in Hokkaido. 2. Results of the field experiment showed that the seed dormancy of Chenopodium album and Echinochloa crus-gdli var. praticoZa was broken more rapidily in the soil layer than on the soil surface, in the period from early November to early December before soil freezing occurred (Table 1.). The seeds which had lost the dormancy were supposedly remained in the field in the state of the enforced dormancy until soil temperature rises. 3. Percent germination of seeds which had lost the dormancy was considerably influenced by the temperature conditions in the dark (Fig. 2). In C. album, the germination rate was very low at any constant temperature, but it increased remarkably when 5℃ was combined with higher temperature in the alternating temperature treatment: that of 5℃/30℃ gave the highest germination. In E. c. var. praticola, very low germination rate at constant temperature of 5℃〜20℃ was increased by the combination with 25℃ and 30℃, and the increase was greater when lower temperature was combined with higher temperature, showing 100% germination at 5℃/30℃. In P. lapathifolium, the reaction of seeds to temperature was similar to C. album at 15゜ and 20℃, and to E. c. var. praticola at 25゜ and 30℃ respectively. Pre-irradiated seeds showed a great increase in germination over the wide range of the temperature conditions examined (Fig. 2). 4. Some possible involvement of light in germination, after the seed dormancy was broken, was experimentally acertained. Most of seeds were stimulated in their germination when an ambient temperature was maintained at 20℃. The most effective wave length of light was 660〜690nm for germlnatron of C album and E. c. var. praticola, while only weak stimulation by 490〜660nm was found in P. lapathifolium seeds. And a brief irradiation such as 400μW at 660nm for 2 seconds was sufficient to elicit germination about 50% of the seeds, and that for 60 seconds was over 70% (Fig. 4). 5. It was demonstrated that the seasonal emergence patterns of these weeds during the time from spring to summer are controlled mainly by the diurnal soil temperature variation in the soil surface layer (Fig. 3). However, an apparent discrepancy between the actual pattern of emergence and the estimated curve of germination was recognized with P. lapathifolium from June onward, and with C. album in October. It was proved to be caused by the secondary dormancy occurring during the period from summer to autumn. 6. It seemed that the ungerminated seeds were in the state of thermodormancy; namely, they re-entered into a dormant state due to high temperature in the summer and the dormancy was terminated by the end of November as the temperature lowered. The seeds buried in shallow soil layer were exposed to the secondary dormancy faster than the deeply buried seeds (Table 2). 7. The population of seeds buried in the soil decreased exponentially, and the decreasing tendency of population in the disturbed soil was more noticeble as compared with seeds buried in the undisturbed soil.
- 日本雑草学会の論文
- 1981-11-25