Annual cycle of Scots pine photosynthesis

Pertti Hari,Steffen Noe,Liisa Kulmala,Veli-Matti Kerminen,Anni Vanhatalo,Tuukka Petäjä,Markku Kulmala,Jaana Bäck

doi:10.5194/acp-17-15045-2017

Abstract

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.

Highlights

The movement of the globe around the sun generates a conspicuous annual cycle of the solar radiation on the earth, and this cycle is especially strong at high latitudes
When we developed the theory of photosynthesis explaining the behaviour in midsummer (Hari et al, 2014), we introduced an axiom stating that the product of the saturating response to the photosynthetically active radiation and CO2 concentration in the stomatal cavity determines the photosynthesis at a point in space and time
When we developed the theory of photosynthesis in midsummer (Hari et al, 2014), we introduced an axiom stating that the product of the saturating response to the photosynthetically active radiation and CO2 concentration in the stomatal cavity determines the photosynthesis at a point in space and time (A1 in Hari et al, 2014)

Summary

Introduction

The movement of the globe around the sun generates a conspicuous annual cycle of the solar radiation on the earth, and this cycle is especially strong at high latitudes. Ambient temperatures respond to the cycle of solar energy input and a strong annual cycle exists in temperature, a bit delayed. These large variations in light and temperature are greatly influencing the distribution of plant species, especially in the northern regions. As a consequence of the seasonal variation in light and temperature, many perennials including deciduous trees have a strong metabolic annual cycle, as they grow new leaves every spring that become senescent in the autumn. The annual cycle is less clear in coniferous trees, they have a period of intensive new foliage growth in the spring and a specific time frame when old needles are senescing in the fall

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