rpmodel (version 1.2.3)

calc_gammastar: Calculates the CO2 compensation point

Description

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

Usage

calc_gammastar(tc, patm)

Value

A numeric value for $\mathrm{\Gamma }\ast$ (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 $\mathrm{\Gamma }\ast (T,p)$ is calculated from its value at standard temperature ($T0=25$deg C) and atmospheric pressure ($p0=101325$ Pa), referred to as $\mathrm{\Gamma }\ast 0$, 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). $\mathrm{\Gamma }\ast 0$ is modified by temperature following an Arrhenius-type temperature response function $f(T,\mathrm{\Delta }Ha)$ (implemented by ftemp_arrh) with activation energy $\mathrm{\Delta }Ha=37830$ J mol-1 and is corrected for atmospheric pressure $p(z)$ (see calc_patm) at elevation $z$. $$\mathrm{\Gamma }\ast =\mathrm{\Gamma }\ast 0f(T,\mathrm{\Delta }Ha)p(z)/p_0$$ $p(z)$ 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

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