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Elevated CO2 Increases Constitutive Phenolics and Trichomes, but Decreases Inducibility of Phenolics in Brassica rapa (Brassicaceae)
Journal of Chemical Ecology, 37 (12): 1332--1340 (15.12.2011)
DOI: 10.1007/s10886-011-0044-z
Аннотация
Increasing global atmospheric CO 2 has been shown to affect important plant traits, including constitutive levels of defensive compounds. However, little is known about the effects of elevated CO 2 on the inducibility of chemical defenses or on plant mechanical defenses. We grew Brassica rapa (oilseed rape) under ambient and elevated CO 2 to determine the effects of elevated CO 2 on constitutive levels and inducibility of carbon-based phenolic compounds, and on constitutive trichome densities. Trichome density increased by 57\% under elevated CO 2 . Constitutive levels of simple, complex, and total phenolics also increased under elevated CO 2 , but inducibility of each decreased. Induction of simple phenolics occurred only under ambient CO 2 . Although induction of complex and total phenolics occurred under both ambient and elevated CO 2 , the damage-induced increases were 64\% and 75\% smaller, respectively, under elevated CO 2 . Constitutive phenolic levels were positively correlated with leaf C:N ratio, and 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 CO 2 . We conclude that B. rapa is likely to exhibit higher constitutive levels of both chemical and mechanical 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 only the second study to report a negative effect of elevated CO 2 on the inducibility of any plant defense.
