Seed dormancy and germination traits of an endangered aquatic plant species, Euryale ferox Salisb. (Nymphaeaceae)

•4°C stratification promoted germination more effectively than 20°C.•Seeds can germinate in both light and darkness.•The optimal germination temperature was 25°C.•Germination frequency at high temperature is higher in light than in darkness.•Smaller seeds show higher germination frequency after extended storage. Populations of Euryale ferox Salisb. have declined throughout its global range because of habitat loss and degradation. The present study aimed to evaluate the influence of storage temperature (4 and 20°C), storage period (0, 90, 180, 270, and 360 days), light condition (light and darkness), germination temperature (constant 10, 15, 20, 25, and 30°C), and seed size (two classes from 0.5cm to less than 1.2cm, and from 1.2cm to less than 1.6cm) on germination of E. ferox seeds. Our results indicated that seeds were dormant when shed and 4°C stratification promoted germination more effectively than 20°C. After stratification at 4°C, the germination frequency of the larger seeds peaked at 90 days’ stratification, whereas the smaller seeds maintained high germination frequencies up to 180 days’ stratification. The different germination responses between smaller and larger seeds may reflect a difference in the rate of induction of dormancy in the annual dormancy cycle. Seeds germinated in both light and darkness, which demonstrated that light is not involved in the regulation of E. ferox seed germination. The optimal temperature for germination was 25°C. Light condition×germination temperature interaction caused significantly higher germination frequency at 30°C in light than in darkness, and the opposite trend at 15°C.