Ecology and Seasonal Development of Ranunculus nipponicus Nakai (Batrachium, Ranunculaceae) in Nonfreezing Watercourses on the Northern Coast of the Sea of Okhotsk

Resumo

The ecology and seasonal development of Ranunculus nipponicus in nonfreezing watercourses on the northern coast of the Sea of Okhotsk (59° N) have been studied. Year-round vegetation and flowering without the formation of a resting stage of the water crowfoot has been reported for the first time for the territory of Russian Federation. During all months of the year, the shoot growth, the formation of young roots, buds, and cleistogamous flowers are observed at an average monthly water temperature of +0.1°C to +5.8°C. The most intensive formation of young roots takes place in February–March and the underwater flowers appear en masse in late March–early April; neither phenomena are associated with an increase in water temperature. Cleistogamous flowering rarely leads to seed ripening, possibly due to a water temperature that is too low.