Seed Germination and Seedling Emergence of Canavalia Lineata (Thunb.) DC. (Fabaceae)

Canavalia lineata (Thunb.) DC. (Fabaceae) is a perennial trailing vine that flowers in the summer, and its seeds are sea-dispersed. It grows under various environmental conditions in coastal areas of the temperate and subtropical regions of Asia. Plant species with a wide distribution tend to differentiate in different environmental conditions; therefore, we conducted this study to find whether C. lineata has regional differentiation in seed germination and seedling emergence. Seeds of C. lineata collected from different areas of Japan were used to compare the seed-floating ability, the effect of low temperature on seed dormancy (0, 2, and 8 months) before germination, and the influence of temperature (4 °C, 15 °C, 20 °C, and 25 °C) on seed germination. Seed-floating tests indicated that many C. lineata seeds can float on the sea without losing their germination ability, and there was no associated regional differentiation. In addition, our results showed that this species could germinate without being exposed to low temperatures, but the timing of germination in such cases was different from that in the seeds that experienced low temperatures. The optimal temperature for C. lineata germination was 20 °C or higher. These analyses did not reveal any regional differentiation. Our results suggest that sea-dispersed seeds of C. lineata that do not lose germination ability for a long period may germinate in relatively warm areas regardless of the presence of low temperature conditions. The study also indicates that as germination of this species requires a relatively high temperature; thus, their distribution has not expanded to the north of Japan.