Journal of Chemical Ecology

, Volume 35, Issue 6, pp 625–634 | Cite as

Visualizing a Plant Defense and Insect Counterploy: Alkaloid Distribution in Lobelia Leaves Trenched by a Plusiine Caterpillar

  • Craig B. Oppel
  • David E. Dussourd
  • Umadevi Garimella


Insects that feed on plants protected by latex canals often sever leaf veins or cut trenches across leaves before feeding distal to the cuts. The insects thereby depressurize the canals and reduce latex exudation at their prospective feeding site. How the cuts affect the distribution and concentration of latex chemicals was not known. We modified a microwave-assisted extraction technique to analyze the spatial distribution of alkaloids in leaves of Lobelia cardinalis (Campanulaceae) that have been trenched by a plusiine caterpillar, Enigmogramma basigera (Lepidoptera: Noctuidae). We produced sharp two dimensional maps of alkaloid distribution by microwaving leaves to transfer alkaloids to TLC plates that were then sprayed with Dragendorff’s reagent to visualize the alkaloids. The leaf prints were photographed and analyzed with image processing software for quantifying alkaloid levels. A comparison of control and trenched leaves documented that trenching reduces alkaloid levels by approximately 50% both distal and proximal to the trench. The trench becomes greatly enriched in alkaloids due to latex draining from surrounding areas. Measurements of exudation from trenched leaves demonstrate that latex pressures are rapidly restored proximal, but not distal to the trench. Thus, the trench serves not only to drain latex with alkaloids from the caterpillar’s prospective feeding site, but also to isolate this section, thereby preventing an influx of latex from an extensive area that likely extends beyond the leaf. Microwave-assisted extraction of leaves has potential for diverse applications that include visualizing the impact of pathogens, leaf miners, sap-sucking insects, and other herbivores on the distribution and abundance of alkaloids and other important defensive compounds.


Plant-insect interactions Leaf-trenching Laticifer Lobeline Microwave-assisted extraction Lobelia cardinalis Enigmogramma basigera 



Many thanks to M.D. Kelley, K.C. Larson, and A.R. Zangerl for helpful advice and to R.D. Noyes and two anonymous reviewers for improving the manuscript. We also gratefully acknowledge financial support from the University of Central Arkansas Research Council (to D.E.D. and U. G.) and Student Research Fund (C.O.), Arkansas Game and Fish Commission Conservation Scholarships (C.O.), and Sigma Xi Grants-in-Aid of Research (C.O.).


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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Craig B. Oppel
    • 1
  • David E. Dussourd
    • 1
  • Umadevi Garimella
    • 1
    • 2
  1. 1.Department of BiologyUniversity of Central ArkansasConwayUSA
  2. 2.Arkansas Center for Mathematics and Science EducationUniversity of Central ArkansasConwayUSA

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