Growth and development of Potamogeton distinctus in an irrigation pond in SW Japan

Growth and development of a population of Potamogeton distinctus were studied over one vegetation period.
The morphological structure of the species is described. Maximum development of the size of shoot complexes occurred in August (up to 12 g dry weight/shoot complex). The plant exhibits a regular growth cycle with continuous horizontal and vertical growth that is illustrated by the development of horizontal shoots, vertical shoots and different plant parts. The lower horizontal shoots allow an extension up to 1.8 m from the point of germination. Before the rainy season in June the 1st to 5th generations of vertical shoots mainly contribute to the standing crop of the plants' stand, and after the rainy season the 5th to 9th generation shoots are predominant. Floating leaves make up the main proportion of biomass during the whole growth cycle. Almost 100% of the shoot complexes were found flowering and producing numerous seeds. Up to 16% of the standing crop are allocated to inflorescence and seeds in August. Turions failed to form that year because of rapid desiccation of the habitat. The observed average lifetime of a vertical shoot is appr. 65 days, the estimated turnover rate is between 2.15 and 2.27.