Cold tolerance of gametophytes and sporophytes of some cool temperate ferns native to Hokkaido

To study the phenological adaptation of the life history of ferns to colder regions, the freezing resistance of gametophytes and sporophytes of 14 cool temperate region ferns native to Hokkaido was evaluated in Sapporo. Moreover, drought tolerance of gametophytes of some cool temperate ferns was elucidated. The mature sporophytes were hardy from −5 to −20 °C in most species. However, gametophytes of most species were tolerant to below −40 °C and regrew into normal gametophytes in a month at room temperature. Most of the gametophytes survived well after dehydration to 2–10% water content. The gametophytic generation was more cold tolerant than the sporophytic one. Thus, the gametophytic generation, rather than the sporophytic, might be the generation that survives cold temperature in the field.