COMPARATIVE-STUDY ON POPULATIONS OF ZOSTERA-MARINA L (EELGRASS) - EXPERIMENTAL GERMINATION AND GROWTH

Seeds of both perennial and (semi-)annual populations of Zostera marina L. originating from different habitats in the southwestern Netherlands and Roscoff (Brittany, France) were germinated and grown under identical circumstances to identify possible genotypically based differences in their population dynamical characters. Individual populations displayed a genotypic background for germination, morphology and flowering, while relative growth rate was considered to be an entirely phenotypic response. Flowering seemed to be related with a higher demand for nitrogen, Perennial versus annual populations did not show genetic variation in any of the response variables investigated. Comparisons with in situ data revealed that presumably the perennial populations in their habitats not fully exploited their potential for (above-ground) growth. Among individual populations, differences in morphology and especially (sexual) reproduction suggest a greater and more complex genotypic background than previously assumed through interpretation of isozyme patterns.