Abstract
The autecology of Cyperus iria L., a principal weed in paddy fields through the world, and a morphologically similar species, C. microiria STEUD., a serious weed in upland fields in Japan, was investigated in an effort to establish effective measures of control. First-run experiments were carried out on seed dormancy, germination, and seedling emergence. The results are summarized as follows:
1) Forty percent of fresh seeds of C. iria germinated, and in only a short period of after-ripening most of the dormant seeds could germinate; C. microiria seeds are dormant, and dormancy could be broken by burying the seeds in upland soil or by storing them at 15°C in a wet condition (Figs, 1, 3).
2) Storage in the darkness at low temperature or in submerged soil caused the seeds of both species to enter into secondary dormancy. Moreover, it was considered that keeping C. microiria seeds in a wet or submerged condition at 25 and 35°C also caused them to enter into secondary dormancy (Figs. 1, 3).
3) Both species seeds required light for germination. However, in the darkness under an alternating temperature (20/35°C) their germination could be stimulated by burying them in upland soil: the longer buried, the more seeds germinated (Fig. 2).
4) There is a difference in the temperature requirement for seed germination between C. iria and C. microiria. Seeds of C. microiria germinated at 25 to 45°C whereas those of C. iria at a wider range of temperature, 15 to 40°C. However, the highest germination percentages of the two species were found at 20/30°C alternating temperature (Table 1).
5) Seeds of both germinated well at the soil surface, but at about one centimeter below the surface, few C. iria seedlings emerged and C. microiria not at all (Table 2).
