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Sagittaria trifolia is a noxious paddy weed in East Asia. This weed propagates both sexually and asexually. Information on the role of sexual reproduction in the spread of herbicide‐resistant gene(s) and control of S. trifolia is important. Therefore, effects of oxygen, light, and temperature on the germination; germination percentages of fresh and stored seeds; and seed dormancy cycles were clarified. Seeds of S. trifolia require hypoxia and light with temperatures above 30/20°C for germination. Germination percentages increased after 1 month of storage on the soil surface. Germination percentages at 35/25°C for seeds submerged in the summer (simulating a well‐drained paddy during winter) and year round (simulating a poorly drained paddy) for 5 months and exhumed on April 7 were 84.7 and 94.4%, respectively, and decreased gradually to 41.3 and 40.0%, respectively, on June 2 (7 months burial). Germination percentages increased again and reached 63.7 and 94.0%, respectively, on July 25 (9 months burial). Seeds that form in summer germinate quickly at high temperatures, and the seedlings form tubers before winter. Thus, once herbicide‐resistant individuals emerge, the resistant gene or genes is/are easily distributed and fixed in the next generation. Autumn plowing and/or the spraying of herbicides is/are effective for controlling this weed. [ABSTRACT FROM AUTHOR]

We examined the seed-germination responses of 27 alpine species with reference to habitat type (fellfield and snowbed), temperature (five regimes), and light requirement. About 70% of species showed>40% germination at warm temperatures without cold stratification. However, a moist-chilling treatment markedly improved the germination percentages in most species, especially under cool conditions. Thus, cold stratification effectively reduced the temperature requirement for germination. Patterns of germination response within species were not consistent between the fellfield and snowbed habitats for species inhabiting both habitats. For interspecific comparisons, there were no significant differences in germination responses to the temperature regimes and the cold stratification between the fellfield and snowbed species. Also, germination speed and the length of germinating period did not differ between fellfield and snowbed species. Most species (86%) showed a requirement for light for germination without cold stratification. Although the extent of the light requirement was reduced after cold stratification in some species, the light requirement of most small-seeded species remained. The combination of cold stratification and the light requirement is a major factor determining the seedling emergence and formation of seed banks in alpine plants. However, habitat-specific patterns of germination traits were less clear, suggesting similar germination traits in fellfield and snowbed plants, at least under controlled conditions in the laboratory. [ABSTRACT FROM AUTHOR]