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Communication at the NABS Annual meeting, Keystone, 2000
(258) EFFECT OF LIGHT AND NUTRIENT AVAILABILITY ON RESOURCE ALLOCATION, GROWTH, CARBON/NITROGEN BALANCE, PHENOLIC CHEMISTRY, AND SUSCEPTIBILITY TO HERBIVORY IN TWO FRESHWATER MACROPHYTES.
G. Cronin2, D.M. Lodge1, and S. Johnson1. 1Department of Biological Sciences, University of Notre Dame, Note Dame, IN 46556, 2Department of Biology, University of Colorado at Denver, Denver, CO 80217
Phenotypic responses of Potamogeton amplifolius and Nuphar advena to different light (7% and 35% of surface irradiance) and nutrient environments were assessed with field manipulation experiments. High nutrient and light availability enhanced the growth of Potamogeton. However, biomass was allocated differently depending on the resource: high light availability resulted in a higher root/shoot ratio, whereas high nutrient availability resulted in a lower root/shoot ratio. Low light availability and high nutrient availability increased the nitrogen content of root and leaf tissue. Root phenolic concentrations were not altered, but leaf phenolics were significantly increased by high light and nutrient availability. None of these changes in tissue constituents resulted in altered palatability to crayfish. The high nutrient treatment killed Nuphar, preventing assessment of phenotypic responses to nutrient availability. High light availability increased overall growth, but this was mainly do to increased growth of the rhizome, resulting in an increased root/shoot ratio. High light tended to increase the production of floating leaves (P=.09) and significantly decreased the production of submersed leaves. High light availability decreased the nitrogen content and increased the phenolic concentration in floating and submersed leaves, but these differences in leaf traits did not result in detectable differences in damage by herbivores.
Presented at 9:30 AM on Thursday, June 1, 2000 in Factors Affecting Algal and Macrophyte Growth I
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