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Carbon cycle
Climate change
Farquhar model
J(max)
Photosynthetic capacity
V-cmax
V-max
Limited photosynthesis
Seasonal variability
Nonlinear inversion
Leaf photosynthesis
Response functions
Spinach leaves
Elevated CO2
Parameters
Dependence
Forest
Abstract:
The Farquhar et al. model Of C-3 photosynthesis is frequently used to study the effect of global changes on the biosphere. Its two main parameters representing photosynthetic capacity, V-cmax and J(max), have been observed to acclimate t o plant growth temperature for single species, but a general formulation has never been derived. Here, we present a reanalysis of data from 36 plant species to quantify the temperature dependence Of V-cmax, and J(max) with a focus on plant growth temperature, i.e. the plants' average ambient temperature during the preceding month. The temperature dependence of V-cmax and J(max) within each data set was described very well by a modified Arrhenius function that accounts for a decrease of V-cmax, and J(max) at high temperatures. Three parameters were optimized: base rate, activation energy and entropy term. An effect of plant growth temperature on base rate and activation energy could not be observed, but it significantly affected the entropy term. This caused the optimum temperature of V-cmax and J(max) to increase by 0.44 degrees C and 0.33 degrees C per 1 degrees C increase of growth temperature. While the base rate of V-cmax and J(max) seemed not to be affected, the ratio J(max) : V-cmax at 25 degrees C significantly decreased with increasing growth temperature. This moderate temperature acclimation is sufficient to doublemodelled photosynthesis at 40 degrees C, if plants are grown at 25 degrees C instead of 17 degrees C. [References: 43]
