calc_kmm | R Documentation |
Calculates the Michaelis Menten coefficient of Rubisco-limited assimilation as a function of temperature and atmospheric pressure.
calc_kmm(tc, patm)
tc |
Temperature, relevant for photosynthesis (deg C) |
patm |
Atmospheric pressure (Pa) |
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, Δ Hkc)
Ko = Ko25 f(T, Δ Hko)
Values Δ Hkc (79430 J mol-1), Δ 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
.
A numeric value for K (in Pa)
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
print("Michaelis-Menten coefficient at 20 degrees Celsius and standard atmosphere (in Pa):") print(calc_kmm(20, 101325))
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