Lignoid chemical defenses in the freshwater macrophyte Saururus cernuus |
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Authors: | Julia Kubanek Mark E Hay Pam J Brown Niels Lindquist William Fenical |
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Institution: | (1) Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0204, USA, US;(2) School of Biology, Georgia Institute of Technology, Atlanta, GA 30332-0230, USA, e-mail: mark.hay@biology.gatech.edu, US;(3) University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC 28557, USA, US |
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Abstract: | Summary. Chemical defense against herbivores has rarely been investigated for freshwater plants, possibly due to the common misconception
that herbivory on aquatic macrophytes is low and would not select for chemical defenses. In previous work, the freshwater
angiosperm Saururus cernuus was shown to be a low preference food for omnivorous crayfish despite its high nutrient value and relatively soft texture.
We used feeding by the crayfish Procambarus clarkii to guide fractionation of the deterrent lipid-soluble extract of this plant, leading to the identification of seven deterrent
lignoid metabolites, (–)-licarin A, (+)-saucernetin, (–)-dihydroguaiaretic acid, (–)-sauriols A and B, (–)-saucerneol, and
(–)-saucerneol methyl ether. Lignans have been implicated in terrestrial plant chemical defenses as insect growth inhibitors,
insect toxins, nematocides, antibacterial, and antifungal agents. However, these activities have rarely been demonstrated
using ecologically relevant methodologies in terrestrial systems, and never before in freshwater systems. The widespread nature
of lignans amongst very distantly related plants, along with their rich diversity of molecular structure, suggests that they
could play a large role in mediating plant-herbivore interactions. In addition to the lignoid compounds we identified, there
were other compounds present in low concentration or unstable compounds that were deterrent, that did not appear to be lignans,
but that we were unable to identify. This plant thus appears to be defended by a complex mixture of natural products.
Received 6 June 2000; revised 23 August 2000; accepted 2 September 2000 |
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Keywords: | , Plant-herbivore interactions –, chemical defense –, lignan –, freshwater macrophyte –, crayfish –,Saururus cernuus -,,,,,Procambarus clarkii |
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