Temperature responses of leaf net photosynthesis: the role of component processes

Abstract

The response of photosynthesis to temperature is a central facet of plant response to climate. Such responses have been found to be highly variable among species and among studies. Understanding this variability is key when trying to predict the effects of rising global temperatures on plant productivity. There are three major factors affecting the response of leaf net photosynthesis to temperature (A(n)-T): (i) photosynthetic biochemistry, (ii) respiration and (iii) vapour pressure deficit (D) and stomatal sensitivity to vapour pressure deficit during measurements. The overall goal of our study was to quantify the relative contribution of each of these factors in determining the response of A(n) to temperature. We first conducted a sensitivity analysis with a coupled photosynthesis-stomatal (A(n)-g(s)) model, using ranges for parameters of each factor taken from the literature, and quantified how these parameters affected the A(n)-T response. Second, we applied the A(n)-g(s) model to two example sets of field data, which had different optimum temperatures (T(opt)) of A(n), to analyse which factors were most important in causing the difference. We found that each of the three factors could have an equally large effect on T(opt) of A(n). In our comparison between two field datasets, the major cause for the difference in T(opt) was not the biochemical component, but rather the differences in respiratory components and in D conditions during measurements. We concluded that shifts in A(n)-T responses are not always driven by acclimation of photosynthetic biochemistry, but can result from other factors. The D conditions during measurements and stomatal responses to D also need to be quantified if we are to better understand and predict shifts in A(n)-T with climate.

From the Arctic Circle to the Canadian prairies – a case study of silver birch acclimation capacity

“…close to present Alberta temperatures) has been found to increase photosynthesis, canopy duration and growth of silver birch under Finnish field conditions (Mäenpää et al 2011). Generally, effects of temperature not only on photosynthetic biochemistry but also on respiratory and stomatal processes are complicated (Lin et al 2012). In silver birch, for example, the response to rising nighttime temperatures consists of a genotypespecific interplay between temperature, light and diurnal oscillations -including growth regulators and feedback from carbon source-sink processes .…”

Description and validation of the Simple, Efficient, Dynamic, Global, Ecological Simulator (SEDGES v.1.0)

“…Although it is well-established that high temperatures (i.e., temperatures above the optimum) limit productivity for individual plants, some of that limitation that has been found empirically may have been due to an indirect effect of temperature on increasing the leaf-to-air vapor pressure deficit (for constant ambient relative humidity), which causes the optimum temperature to be lower than when the vapor pressure deficit is held fixed (Lin et al, 2012). An even more important point is that a high temperature limitation reflects more the inability of plants that are adapted to a given en- (Kleidon, 2006b) and the (Mueller et al, 2013) reference dataset for the 1989-2005 period over non-glaciated land.…”

Description and Validation of the Simple, Efficient, Dynamic, Global, Ecological Simulator (SEDGES v.1.0)

“…Although it is well-established that high temperatures (i.e. temperatures above the optimum) limit productivity for individual plants, some of that limitation that has been found empirically may have been due to an indirect effect of temperature on increasing leaf-to-air vapor pressure deficit (for constant ambient relative humidity), which causes optimum temperature to be lower than when vapor 30 pressure deficit is held fixed (Lin et al, 2012). An even more important point is that high temperature limitation reflects more the inability of plants that are adapted to a given environment to perform equally well under all conditions that they might face in that environment and less an intrinsic barrier for plant life at that location to adapt to a given high temperature regime (via some combination of species migrations, natural selection, evolution, and/or acclimation).…”