Warming does not stimulate mitochondrial respiration and it responds to leaf carbohydrates availability in soybean plants grown under elevated CO2 concentrations

Abstract:

There is a lack of understanding on the mechanism underlying the response of mitochondrial respiration (Rs) to the single and combined effects of increasing CO₂ concentration ([CO₂]) and warming. We investigated the response of Rs to the single and combined effects of elevated [CO₂] and warming in soybean plants over a complete growing season using Temperature by Free Air CO2 enrichment technology under field conditions. The treatments were: control, elevated [CO₂] (eC), high temperature (eT), and elevated [CO₂]+high temperature (eT+eC). Given that photosynthetic rates in eT+eC grown plants were not higher than in plants grown under eC, we hypothesized that Rs would increase only slightly in plants grown under eT+eC compared to eC plants, due to the increase of temperature. Contrary to our prediction, our preliminary results showed that plants grown under the warming treatments had low Rs, thus eT+eC had lower Rs than eC. The response of Rs to these factors was consistent at two different plant high levels (canopy and five nodes down the canopy). Changes in Rs were explained by variations in the carbohydrate content. Our results indicate that the response of Rs to changes in [CO₂] and temperature will depend on the carbohydrate availability of plant tissues and thus on how photosynthesis is affected by this environmental factors.