Thursday, August 9, 2007

PS 62-99: Does atrazine exposure stimulate fluctuating asymmetry in silver maple (Acer saccharinum) seedlings?

Marilyn C. Caldwell, Kurt E. Schulz, and Luci Ann P. Kohn. Southern Illinois University Edwardsville

Atrazine is one of the most widely applied agricultural herbicides in the Midwestern U.S.  Although its use is banned in much of Europe, comparatively little has been done to assess its ecological impacts on a broad scale.  Toward this end, simple techniques to identify organisms experiencing atrazine exposure would be useful.  Fluctuating asymmetry (FA), random deviations from bilateral symmetry, has been shown to increase in a wide array of plants and animals in response to environmental stress.  We subjected one year old silver maple seedlings (a common species along regional watercourses) representing 15 maternal genotypes to two realistic regimes of atrazine exposure in irrigation water.  We compared the sizes and shapes of subsequently formed pairs of leaves at single nodes, as well as the left and right sides of representative leaves to detect FA.  ANOVA revealed differences in the sizes and shapes of leaves from different maternal lines, but showed no effect of atrazine treatment, and no evidence of FA.  Comparisons of traits on the left and right sides of leaves showed no treatment effects, but maternal differences in traits, and preliminary evidence of FA.  Subsequent analysis revealed directional symmetry in one trait and evidence of FA related to the maternal parent in another trait.  

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