gammastar {rpmodel}

Calculates the CO2 compensation point

Description

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

Usage

gammastar(tc, patm)

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 patm) at elevation z.

\Gamma* = \Gamma*0 f(T, \Delta Ha) p(z) / p_0

p(z) is given by argument patm.

Value

A numeric value for \Gamma* (in Pa)

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(gammastar(20, 101325))