Karowe, David , Grubb, Christopher .
Effects of Elevated CO2 on Inducibility of Phenolic Defenses in Brassica rapa.
Increasing global atmospheric CO2 has been shown to affect important plant traits, including constitutive levels of defensive compounds. However, very little is known about the effects of elevated CO2 on the inducibility of chemical defenses or on plant mechanical defenses. We grew Brassica rapa (oilseed rape) under ambient (379 ppm) and elevated (744 ppm) CO2 to determine the effects of elevated CO2 on constitutive levels and inducibility of carbon-based phenolic compounds, and on constitutive trichome densities. Constitutive levels of simple, complex, and total phenolics increased under elevated CO2. However, phenolics were less inducible under elevated CO2, so post-damage levels were similar under ambient and elevated CO2. Constitutive phenolic levels were positively correlated with leaf C:N ratio, but inducibility was positively correlated with leaf N (and negatively correlated with leaf C:N ratio), as would be expected if inducibility were constrained by nitrogen availability under elevated CO2. We conclude that B. rapa is likely to exhibit higher levels of both chemical and mechanical constitutive defenses in the future, but is also likely to be less able to respond to herbivore damage by inducing phenolic defenses. To our knowledge, this is the first demonstration of a negative effect of elevated CO2 on the inducibility of any plant defense.
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David Karowe research homepage
1 - Western Michigan University, Biological Sciences, 3155 Wood Hall, Kalamazoo, MI, 49008-5410, USA
2 - University of Michigan, School of Natural Resources and Environment, Ann Arbor, MI, 48109, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 28th, 2008
Time: 3:45 PM