Thermal acclimation of photosynthesis and respiration in Eucalyptus pauciflora of varying growth temperatures in Kosciuszko National Park

Abstract

The processes of photosynthesis and respiration in plants are largely responsible for levels of atmospheric CO₂ globally. Predicting future output and uptake of carbon by plants is therefore crucial for developing accurate climate change models. The effect of temperature acclimation on photosynthesis and respiration rates in plants is currently not considered in global carbon models. Therefore, current terrestrial carbon models may be overestimating carbon release from plants as acclimation to higher growth temperatures in many species leads to a fall in respiration and an increase in the temperature at which photosynthesis is optimised. In this study, the ability of photosynthesis and respiration in snow gums (Eucalyptus pauciflora) to acclimate was tested. Leaf samples were taken from trees at four different elevations, and rates of photosynthesis and respiration were measured at 25°C using a licor 6400 Gas Exchange System. Temperatures of each collection site (growth temperatures) were measured hourly over three days using temperature and humidity data loggers (ibuttons). Results were analysed by comparing growth temperature of the samples to the rate of respiration and photosynthesis at 25°C. Lower temperatures correlated to low rates of photosynthesis and higher rates of respiration, when measured at the common temperature of 25°C. These results indicate that respiration and photosynthesis in snow gums does acclimate to ambient temperature, and this allows for the development of more accurate climate change models.