PARENT SESSION
Posters P3B Photosynthetic acclimation: Ecophysiology, diverse environments. Abstracts (479-522)

Variation in the degree of photosynthetic and respiratory acclimation to long-term changes in temperature. Catherine Campbell^*,1, Lindsey Atkinson¹, Joana Zaragoza Castells¹, Vaughan Hurry², Owen Atkin¹, ¹ Department of Biology, Area 2, York, United Kingdom²

ABSTRACT- Understanding the effects of changing temperature on photosynthesis and respiration is critical to predicting the responses of ecosystems to global change. The rate of carbon assimilation and respiration may have an impact on the rate of atmospheric [CO₂] increase. Both processes respond strongly to changes in temperature, but the long-term effects of temperature change depend upon the degree to which plants can acclimate by adjusting the rates of photosynthesis and respiration to compensate for change in temperature. The overall objective of our work is to assess the extent to which the sensitivity of photosynthesis and respiration to long-term changes in temperature varies systematically within and among contrasting plant species. Previous work with Arabidopsis thaliana, which has relatively short-lived leaves, suggested that the development of new leaves is required for full acclimation. However, other species may respond differently, e.g. plants with longer-lived leaves, or a slower relative growth rate. In the current study, gas exchange measurements were conducted on fully expanded leaves of plants with contrasting relative growth rates and specific leaf areas from a range of genera. All were transferred from growth at 21 ^oC to lower and higher temperature chambers, set to 7, 14, and 28 ^oC; controls were kept at 21 ^oC. Photosynthetic and respiratory rates were measured immediately after transfer, 10 days after transfer, and again after the development of new leaves, 30 to 60 days later. Our results show that pre-existing leaves of Quercus ilex are capable of a high degree of acclimation following 60 days of exposure to a new thermal regime. These results demonstrate that the production of new leaves is not necessary for full acclimation in long-lived leaves, and that acclimation may take a considerable length of time. The temperature acclimation responses of the contrasting species in other genera will also be discussed.

KEY WORDS: acclimation, temperature, respiration