Life-cycles of three populations of Potamogeton pectinatus L. at different degrees of wave exposure in the Askö area, Northern Baltic proper

Abstract

Potamogeton pectinatus L. populations were studied at three stations over an annual cycle. The maximum standing crop of 17.5 g dry weight (wt.) m −2 was recorded a the most sheltered station, decreasing slightly at the intermediate station to 15.8 g dry wt.m −2, and being only 4.8 g dry wt.m −2 at the most exposed station. Flowering and seed production occurred at all three stations. The maximum proportion of dry weight allocated to reproduction was higher at the more exposed stations (4%), while at the sheltered station only 1% was allocated to reproductive parts. The number of overwintering tubers produced per m 2 decreased from 115 per m 2 to 45 per m 2 with lowered exposure. Conversely, the number of flowers per inflorescence and flowers per m 2 was highest at the most sheltered station, decreasing from 9 to 6 and 945 to 672 per m 2, respectively, with increasing exposure. No definite trend could be found for seed production, which was highly variable and dependent on a successful period of fertilization during calm weather. At the sheltered locality more resources were allocated to vegetative shoots and rhizomes which were also able to overwinter. The resource allocation of Potamogeton pectinatus seems to be strongly influenced by environmental factors. This is discussed in relation to current reproductive strategy concepts.