calc_kmm {rpmodel}

Calculates the Michaelis Menten coefficient for Rubisco-limited photosynthesis

Description

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

Usage

calc_kmm(tc, patm)

Arguments

tc

Temperature, relevant for photosynthesis (deg C)

patm

Atmospheric pressure (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.

Value

A numeric value for K (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("Michaelis-Menten coefficient at 20 degrees Celsius and standard atmosphere (in Pa):")
print(calc_kmm(20, 101325))