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C4 Arrhenius parameters with no temperature dependence

c4_arrhenius_no_temp.Rd

Arrhenius parameters that specify a flat temperature response (in other words, no dependence on temperature) for important C4 photosynthetic parameters, intended to be passed to the calculate_arrhenius function.

Usage

c4_arrhenius_no_temp

Format

List with 9 named elements that each represent a variable whose temperature-dependent value can be calculated using the Arrhenius equation:

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

  • Vpmax_norm: The maximum rate of PEP carboxylase activity (Vpmax) normalized to its value at 25 degrees C.

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

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

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

  • Kp: The Michaelis-Menten constant of PEP carboxylase.

  • gamma_star: Half the reciprocal of rubisco specificity.

  • ao: The ratio of solubility and diffusivity of O2 to CO2.

  • gmc: The mesophyll conductance to CO2 diffusion.

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

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

Here, the activation energy values (Ea) are all set to 0, which means that the values will not depend on temperature. The Arrhenius scaling factors c are chosen to reproduce the parameter values at 25 degrees C as specified in von Caemmerer (2021). (See c4_arrhenius_von_caemmerer.)

References:

  • von Caemmerer, S. "Updating the steady-state model of C4 photosynthesis" Journal of Experimental Botany 72, 6003–6017 (2021) [doi:10.1093/jxb/erab266 ].