Germination characteristics of Sagittaria trifolia.

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]