Life histories of two clonal populations of stratiotes aloides L

Life-history characteristics of two north Swedish populations of Stratiotes aloides L. are compared. One population consists of an emergent phenotype, living in a nutrient-rich lake. The other population is entirely formed by submersed plants, living in a nutrient-poor, riverside lagoon. Plants from each population transplanted to the other habitat showed that the emergent form was able to develop a submersed habit, whereas no significant change was observed in the submerged form. The life cycle of the species is characterized by a winter-green period, during which the emergent form retained 36% and the submerged form 63% of its maximum biomass, respectively. Leaf turnover of both forms followed the same pattern, with successively increasing losses of old leaves during the growing season, resulting in an overwintering rosette made up of freshly-produced leaves.