Modification of Photosynthesis Temperature Response by Long-Term Growth in Elevated CO2 and Temperature in Wheat Field Crops

Abstract

To test whether long-term growth in elevated CO2 and temperature modifies photosynthesis temperature response, wheat (Triticum aestivum L.) was grown in ambient CO2 (370μmol mol−1) and elevated CO2 (700 μmol mol−1) combined with ambient and 4°C warmer temperatures, using temperature gradient chambers in the field. Flag leaf photosynthesis was measured at temperatures ranging from 20°C to 35°C and 330 μmol mol−1 or lower CO2 concentrations between ear emergence and anthesis. The maximum rate of carboxylation was determined in vitro in the first year of the experiment and from the photosynthesis- intercellular CO2 response in the second year. Growth temperature had no effect on flag leaf photosynthesis in plants grown in ambient CO2, while it increased photosynthesis in elevated growth CO2 without modifying the response of photosynthesis to measurement temperatures. Growth in elevated CO2 increased the temperature response (activation energy) of the maximum rate of carboxylation. The results provide field evidence that growth under CO2 enrichment enhances the response of Rubisco activity to temperature in wheat.