| Popis: |
Samples of Elodea canadensis Rich. in Michx. were investigated to determine the relationship between nutrient pollution, element constitution, and variation in morphological expression. Systematic samplings from twenty-four stations in two Pennsylvania streams were analysed chemically by emission spectrometry and morphologically by detailed measurements of several root, shoot, and leaf characteristics. These data were correlated statistically and compared to specific taxonomic descriptions available in the literature and to three levels of environmental nutrient pollution. In general, the samples varied widely in element content and morphological characteristics. Some of the morphological variation reported exceeds the conventional limits established for the species. Significant correlations were obtained that suggest causal relationships between the concentration of certain element constituents and the levels of other elements detected, the concentration of specific element constituents and the expression of several morphological characters, and the expression of morphological characters one to another. A causal relationship between nutrient pollution and morphology is clearly indicated, yet final conclusions cannot be made in lieu of additional experiments involving more rigorous environmental controls. |
