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Do defoliation and subsequent phytochemical responses reduce future herbivory on oak trees?
1Department of Zoology, Arizona State University, 85287-1501, Tempe, Arizona.
Journal of Chemical Ecology
|November 21, 2013
Summary
Perennial plants do not become less susceptible to herbivores after defoliation. New foliage, despite increased tannins, experienced higher herbivory, challenging the defense hypothesis.
Area of Science:
- Plant ecology
- Chemical ecology
- Plant-herbivore interactions
Background:
- Perennial plants are hypothesized to increase chemical defenses in new foliage after herbivory.
- This defense mechanism aims to protect against future herbivore damage within a growing season.
Purpose of the Study:
- To test if induced phytochemical changes in Quercus emoryi foliage reduce subsequent herbivory after defoliation.
- To investigate changes in protein and tannin levels in response to simulated herbivory.
Main Methods:
- Manual removal of primary foliage from Quercus emoryi branches at two seasonal time points.
- Monitoring of protein and tannin content in new foliage.
- Quantification of herbivory levels on refoliated versus control branches.
Main Results:
- New foliage exhibited 2.5 times higher hydrolyzable tannin content compared to mature control leaves.
- Condensed tannins were lower, and protein content was temporarily higher in new leaves.
- Refoliated branches experienced greater herbivory than control branches, despite increased tannins.
Conclusions:
- The study did not support the hypothesis that induced phytochemical changes protect perennial plants from subsequent herbivory within a season.
- Factors like lower leaf toughness and higher water content in new foliage may override chemical defenses.
- New foliage remains susceptible to herbivory irrespective of its production timing after defoliation.
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