Nesman, Rory , Berry, Eric .
A Brine Shrimp Bioassay Comparing Anti-herbivory Compounds in the Endangered Wildflower Senna hebecarpa and Four Other Temperate Wildflowers.
Northern Wild Senna (Senna hebecarpa) is an endangered wildflower that was once widespread throughout much of New England. The species thrives in moist alluvial soils within disturbed habitats such as stream banks, roadside ditches, and meadows. Although there have been several hypothesized causes to the species decline, one factor that does not appear to be contributing is excessive herbivory. We found little evidence of herbivory within a wild population at our field site in Amherst, NH; an observation that is consistent with other reports of cows “shunning” the plant in pastures. Anti-herbivory compounds have not been extracted and identified for S. hebecarpa, but other Senna species are know to be purgatives or mild laxatives due to the presence of cathartic acid, which is eliminated by digestion. In our study, we examined the anti-herbivore defenses in leaves of S. hebecarpa using a brine shrimp bioassay. Brine shrimp (Artemia salina) are one of the most commonly used bioassays for plant toxins because they can be considered “naive” organisms with respect to plant toxins in that they have not been exposed to land plants during their evolutionary history. We exposed the shrimp to extracts of leaf tissue over a broad range of concentrations in order to construct a dose response curve, from which we calculated the concentration of extract that kills 25% of shrimp within 24 hours (lethal concentration = LC25) and 50% within 48 hours (LC50). We compared the findings for S. hebecarpa to other wildflowers that are found in similar disturbed habitats, two of which are known to produce substantial anti-herbivory compounds (Asclepias syriaca, Solanum dulcamara) and two that are likely less toxic (Phytolacca americana, Polygonum pensylvanicum). Results from our experiment indicate that the phytotoxicity of S. hebecarpa leaves is relatively high, producing LC values comparable to those we recorded for A. syriaca and S. dulcamara, both of which are chemically well-defended from herbivores.
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1 - Saint Anselm College, 100 Saint Anselm Drive, Manchester, NH, 03102, USA
2 - Saint Anselm College, Biology, 100 Saint Anselm Drive, Manchester, NH, 03102, USA
brine shrimp bioassay
Presentation Type: Poster:Posters for Topics
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM