PARENT SESSION
Poster Session # 13: Biogeochemistry, Photosynthesis, and Respiration.

Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Stress reponses of Chenopodium album and Amaranthus retroflexus to heat stress grown in elevated CO₂ and temperature.

Hamilton, E William^*,1, Heckathorn, Scott², ¹ Washington and Lee University, Lexington, VA² Syracuse University, Syracuse, NY

ABSTRACT- The predicted increase in global carbon dioxide concentrations and temperatures with associated increased frequency of temperature extremes will have a significant impact on plant populations. This experiment quantified the responses of Chenopodium album (C₃) and Amaranthus retroflexus (C₄) to elevated CO₂ and temperature and chronic heat stress (HS). The experiment consisted of 2-CO₂ concentrations (350 and 700 ppm) x 2 growth temperatures (16:24 and 22:30 °C night:day) x 2 temp treatments (Control and HS at 42°C after one month of growth in treatments). We quantified net photosynthesis and a set of stress responses related to heat and oxidative stress tolerance. The stress responses of interest were small heat-shock proteins, ascorbate (Vitamin C), Cu/Zn superoxide dismutase and catalase. Photosynthesis was stimulated by elevated CO₂ in Chenopodium at low growth temperatures but not at elevated growth temperatures and CO₂ and there were no significant effects in Amaranthus. Production of stress responses increased in Chenopodium grown in 350 ppm CO₂ when grown at low temperatures and heat stressed, but Chenopodium grown at elevated temperatures and elevated CO₂ had reduced production. Amaranthus had increased production of stress proteins in both growth temperature treatments when heat stresses and production was highest at 700 ppm CO₂. The results suggest that the interaction of elevated CO₂ and temperatures and temperature extremes may negatively impact Chenopodium populations and potentially other C3 herbaceous perennials and that Amaranthus will not be negatively effected and potentially other C4 species.

Key words: Amaranthus retroflexus, elevated CO₂ and temperature, Chenopodium album, heat stress