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C3 Arrhenius parameters from Sharkey et al.

c3_arrhenius_sharkey.Rd

Arrhenius parameters describing the temperature response of important C3 photosynthetic parameters, intended to be passed to the calculate_arrhenius function.

Usage

c3_arrhenius_sharkey

Format

List with 6 named elements that each represent a variable whose temperature-dependent value can be calculated using the Arrhenius equation:

  • Kc: The Michaelis-Menten constant for rubisco carboxylation.

  • Ko: The Michaelis-Menten constant for rubisco oxygenation.

  • Gamma_star: The value of CO2 partial pressure in the chloroplast at which no assimilation occurs in the absence of respiration.

  • Vcmax_norm: The maximum rate of rubisco carboxylation (Vcmax) normalized to its value at 25 degrees C.

  • J_norm: The electron transport rate (J) normalized to its value at 25 degrees C.

  • RL_norm: The respiration rate (RL) normalized to its value at 25 degrees C.

In turn, each of these elements is a list with 3 named elements:

  • c: the (dimensionless) Arrhenius scaling factor.

  • Ea: the activation energy in kJ / mol.

  • units: the units of the corresponding variable.

Source

Some of these parameters (RL, Vcmax, and J) are normalized to their values at 25 degrees C. These variables include _norm in their names to indicate this.

The remaining parameters (Gamma_star, Kc, and Ko) are not normalized because they are assumed to not vary significantly between species.

Arrhenius parameters were obtained from Sharkey et al. (2007). In this publication, gas concentrations are expressed as partial pressures (in Pa or kPa) rather than mole fractions (micromol / mol or mmol / mol). However, for consistency with c3_arrhenius_bernacchi, here we prefer to use mole fractions.

To convert a concentration expressed as a partial pressure (P; in Pa) to a concentration expressed as a mole fraction (C; in micromol / mol), we need a value for atmospheric pressure; we will use the typical value of 101325 Pa. Then C = P / 101325 * 1e6 or C = P * cf, where cf = 1e6 / 101325 is a conversion factor. The same correction can be used to convert kPa to mmol / mol. The value of cf can be accessed using PhotoGEA:::c_pa_to_ppm.

References:

  • Sharkey, T. D., Bernacchi, C. J., Farquhar, G. D. & Singsaas, E. L. "Fitting photosynthetic carbon dioxide response curves for C3 leaves" Plant, Cell & Environment 30, 1035–1040 (2007) [doi:10.1111/j.1365-3040.2007.01710.x ].