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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 24 | Copyright

Special issue: Pan-Eurasian Experiment (PEEX)

Atmos. Chem. Phys., 17, 15045-15053, 2017
https://doi.org/10.5194/acp-17-15045-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 20 Dec 2017

Research article | 20 Dec 2017

Annual cycle of Scots pine photosynthesis

Pertti Hari1, Veli-Matti Kerminen2, Liisa Kulmala1, Markku Kulmala2, Steffen Noe3, Tuukka Petäjä2, Anni Vanhatalo1, and Jaana Bäck1 Pertti Hari et al.
  • 1Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 Helsinki, Finland
  • 2Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
  • 3Department of Plant Physiology, Estonian University of Life Sciences, Fr.R. Kreutzwaldi 1, 51014 Tartu, Estonia

Abstract. Photosynthesis, i.e. the assimilation of atmospheric carbon to organic molecules with the help of solar energy, is a fundamental and well-understood process. Here, we connect theoretically the fundamental concepts affecting C3 photosynthesis with the main environmental drivers (ambient temperature and solar light intensity), using six axioms based on physiological and physical knowledge, and yield straightforward and simple mathematical equations. The light and carbon reactions in photosynthesis are based on the coherent operation of the photosynthetic machinery, which is formed of a complicated chain of enzymes, membrane pumps and pigments. A powerful biochemical regulation system has emerged through evolution to match photosynthesis with the annual cycle of solar light and temperature. The action of the biochemical regulation system generates the annual cycle of photosynthesis and emergent properties, the state of the photosynthetic machinery and the efficiency of photosynthesis. The state and the efficiency of the photosynthetic machinery is dynamically changing due to biosynthesis and decomposition of the molecules. The mathematical analysis of the system, defined by the very fundamental concepts and axioms, resulted in exact predictions of the behaviour of daily and annual patterns in photosynthesis. We tested the predictions with extensive field measurements of Scots pine (Pinus sylvestris L.) photosynthesis on a branch scale in northern Finland. Our theory gained strong support through rigorous testing.

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We developed a theory on the seasonal behaviour of photosynthesis in natural conditions and tested the theory with intensive measurements. Light, temperature, water vapor and CO2 concentration explained the daily variation in photosynthesis, and the physiological state of the photosynthetic machinery explained the annual pattern of photosynthesis. The theory explained about 95 % of the variance of photosynthesis measured with chambers in the field in northern Finland.
We developed a theory on the seasonal behaviour of photosynthesis in natural conditions and...
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