August 4, 2019
A global analysis of triose phosphate limitation of CO2 assimilation concludes that, contrary to current terrestrial biosphere model representations, the process does not limit CO2 assimilation.
Photosynthesis is represented in terrestrial biosphere models (TBMs) as the minimum of three processes: carboxylation, electron transport, and triose phosphate utilization (TPU). Model representation of TPU has been shown to be an important limiting process in current TBMs. This study showed that this assumption is false and that TPU is unlikely to limit photosynthesis at current ambient carbon dioxide (CO2) concentration.
This work emphasizes the need to better understand TPU limitation and to improve representation of TPU in TBMs. Current representation will result in lower modeled CO2 assimilation, particularly at high latitudes.
The TPU rate has been identified as one of the processes that can limit terrestrial plant photosynthesis. However, researchers lack a robust quantitative assessment of TPU limitation of photosynthesis at the global scale. As a result, TPU, and its potential limitation of photosynthesis, is poorly represented in TBMs. This research showed that TPU does not limit leaf photosynthesis at the current ambient atmospheric CO2 concentration. Furthermore, data showed that the light-saturated photosynthetic rates of plants growing in cold environments are not more often limited by TPU than those of plants growing in warmer environments. In addition, the work demonstrated that the instantaneous temperature response of TPU is distinct from the temperature response of carboxylation capacity, which is currently used to scale TPU in terrestrial biosphere models.
BER Program Manager
U.S. Department of Energy Office of Science, Office of Biological and Environmental Research
Earth and Environmental Systems Sciences Division (SC-33.1)
Environmental System Science
Brookhaven National Laboratory
Associated data collection and other contributions by AR were funded by the Next-Generation Ecosystem Experiments (NGEE)–Arctic project, which is supported by the Terrestrial Ecosystem Science program of the Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science.
Kumarathunge, D. P., B. E. Medlyn, J. E. Drake, A. Rogers, and M. G. Tjoelker. “No evidence for triose phosphate limitation of light-saturated leaf photosynthesis under current atmospheric CO2 concentration.” Plant, Cell & Environment 42(12), 3241–52 (2019). [DOI:10.1111/pce.13639].