calc_gammastar: Calculates the CO2 compensation point

Description

Calculates the photorespiratory CO2 compensation point in absence of dark respiration, $\Gamma*$ (Farquhar, 1980).

Usage

calc_gammastar(tc, patm)

Value

A numeric value for $\Gamma*$ (in Pa)

Arguments

tc: Temperature, relevant for photosynthesis (degrees Celsius)
patm: Atmospheric pressure (Pa)

Details

The temperature and pressure-dependent photorespiratory compensation point in absence of dark respiration $\Gamma* (T,p)$ is calculated from its value at standard temperature ($T0 = 25 $deg C) and atmospheric pressure ($p0 = 101325$ Pa), referred to as $\Gamma*0$, quantified by Bernacchi et al. (2001) to 4.332 Pa (their value in molar concentration units is multiplied here with 101325 Pa to yield 4.332 Pa). $\Gamma*0$ is modified by temperature following an Arrhenius-type temperature response function $f(T, \Delta Ha)$ (implemented by ftemp_arrh) with activation energy $\Delta Ha = 37830$ J mol-1 and is corrected for atmospheric pressure $p(z)$ (see calc_patm) at elevation $z$. $$ \Gamma* = \Gamma*0 f(T, \Delta Ha) p(z) / p_0 $$ $p(z)$ is given by argument patm.

References

Farquhar, G. D., von Caemmerer, S., and Berry, J. A.: A biochemical model of photosynthetic CO2 assimilation in leaves of C 3 species, Planta, 149, 78–90, 1980.

Bernacchi, C. J., Singsaas, E. L., Pimentel, C., Portis, A. R. J., and Long, S. P.:Improved temperature response functions for models of Rubisco-limited photosyn-thesis, Plant, Cell and Environment, 24, 253–259, 2001

Examples

Run this code

print("CO2 compensation point at 20 degrees Celsius and standard atmosphere (in Pa):")
print(calc_gammastar(20, 101325))

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