PARENT SESSION
Poster Session #49: Elevated CO₂ II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

The effects of elevated carbon dioxide and nitrogen availability on plant and insect herbivore performance.

Sudderth, Erika^*,1, Bazzaz, F¹, ¹ Harvard University, Cambridge, MA

ABSTRACT- Insect herbivory is a carbohydrate sink, which has been hypothesized to affect the photosynthetic acclimation of plants to elevated CO₂. It has also been demonstrated that there are important interactions between the response of plants to nitrogen and to elevated CO₂. However, the combined effects of nitrogen and CO₂ on both plant and insect performance have rarely been measured simultaneously. The effects of elevated CO₂ and nitrogen availability on the performance of two phloem-feeding insect herbivores (Macrosiphum euphorbiae and Metopolophium dirhodum) and their host plant (Solanum dulcamara) were investigated. The factorial experiment was conducted in six environmental growth chambers, using ambient (370ppm) and elevated (700ppm) CO₂ concentrations, and nitrogen concentrations of 1 and 3 mM NO3. Nitrogen availability significantly increased plant biomass at both ambient and elevated CO₂, with or without aphids present (p <0.0001). There was no significant effect of elevated CO₂ when there was low nitrogen availability, however CO₂ significantly increased plant biomass when there was high nitrogen availability (CO₂*NO3 interaction; p=0.036). Elevated CO₂ did not affect the number of aphids per plant, while higher nitrogen availability significantly increased the number of aphids per plant (p=0.046). The availability of nitrogen is important in controlling both plant response to elevated CO₂ and aphid performance on plants grown under different CO₂ conditions.

KEY WORDS: Elevated CO2, Macrosiphum euphorbiae , Metopolophium dirhodum, Solanum dulcamara