SEED OUTPUT AND THE SEED BANK IN VALLISNERIA-AMERICANA (HYDROCHARITACEAE)

Seed banks and sexual reproduction are known to be significant in colo nization and re-establishment of some aquatic macrophyte communities. For highly clonal aquatic macrophytes, however, there is a lack of inf ormation on seed production and seed fate as compared with annual sexu al species. The seed bank for three populations of Vallisneria america na in the Huron-Erie corridor of the Great Lakes was sampled and quant ified in the spring of 1994, and related to seed production in the pre vious season at these sites. Seed deposition rates during 1994 were al so assessed. Sites varied in the proportion of plants flowering and in their tertiary sex ratios, but did not differ in seed numbers produce d per unit area. The size of the seed bank was not significantly relat ed to the previous season's seed output, and estimates of seed deposit ion in the following year tended to be approximately tenfold greater t han seed densities found in the seed bank. The stages between seed pro duction and subsequent seed germination are generally very dynamic, wi th dispersal, mortality, and predation as likely regulating factors. T he potential for seedling establishment in V. americana needs to be as sessed more fully before the role of seeds in population processes can be determined.