Calculates the Michaelis Menten coefficient for Rubisco-limited photosynthesis

Source: R/subroutines.R

Calculates the Michaelis Menten coefficient of Rubisco-limited assimilation as a function of temperature and atmospheric pressure.

kmm(tc, patm)

Arguments

tc

Temperature, relevant for photosynthesis (deg C)
patm

Atmospheric pressure (Pa)

Value

A numeric value for \(K\) (in Pa)

Details

The Michaelis-Menten coefficient \(K\) of Rubisco-limited photosynthesis is determined by the Michalis-Menten constants for O2 and CO2 (Farquhar, 1980) according to: $$ K = Kc ( 1 + pO2 / Ko) $$ where \(Kc\) is the Michaelis-Menten constant for CO2 (Pa), \(Ko\) is the Michaelis-Menten constant for O2 (Pa), and \(pO2\) is the partial pressure of oxygen (Pa), calculated as \(0.209476 p\), where \(p\) is given by argument patm. \(Kc\) and \(Ko\) follow a temperature dependence, given by the Arrhenius Equation \(f\) (implemented by ftemp_arrh): $$ Kc = Kc25 f(T, \Delta Hkc) $$ $$ Ko = Ko25 f(T, \Delta Hko) $$ Values \(\Delta Hkc\) (79430 J mol-1), \(\Delta Hko\) (36380 J mol-1), \(Kc25\) (39.97 Pa), and \(Ko25\) (27480 Pa) are taken from Bernacchi et al. (2001) and have been converted from values given therein to units of Pa by multiplication with the standard atmosphere (101325 Pa). \(T\) is given by the argument tc.

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("Michaelis-Menten coefficient at 20 degrees Celsius and standard atmosphere (in Pa):")

#> [1] "Michaelis-Menten coefficient at 20 degrees Celsius and standard atmosphere (in Pa):"
print(kmm(20, 101325))

#> [1] 46.09928