c3_temperature_param_sharkey: C3 temperature response parameters from Sharkey et al.

In PhotoGEA: Photosynthetic Gas Exchange Analysis

C3 temperature response parameters from Sharkey et al.

Description

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

Usage

c3_temperature_param_sharkey

Format

List with 11 named elements that each represent a variable whose temperature-dependent value can be calculated using an Arrhenius equation or a polynomial equation:

• Gamma_star_at_25: The value of chloroplastic CO2 concentration at which CO2 gains from Rubisco carboxylation are exactly balanced by CO2 losses from Rubisco oxygenation (Gamma_star) at 25 degrees C.

• Gamma_star_norm: Gamma_star normalized to its value at 25 degrees C.

• gmc_norm: The mesophyll conductance to CO2 diffusion (gmc) normalized to its value at 25 degrees C.

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

• Kc_at_25: The Michaelis-Menten constant for rubisco carboxylation (Kc) at 25 degrees C.

• Kc_norm: Kc normalized to its value at 25 degrees C.

• Ko_at_25: The Michaelis-Menten constant for rubisco oxygenation (Ko) at 25 degrees C.

• Ko_norm: Ko normalized to its value at 25 degrees C.

• RL_norm: The rate of non-photorespiratory CO2 release in the light (RL) normalized to its value at 25 degrees C.

• Tp_norm: The maximum rate of triose phosphate utilization (Tp) normalized to its value at 25 degrees C.

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

In turn, each of these elements is a list with at least 2 named elements:

• type: the type of temperature response

• units: the units of the corresponding variable.

Source

Many of these parameters are normalized to their values at 25 degrees C. These variables include _norm in their names to indicate this.

Response 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_temperature_param_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) [\Sexpr[results=rd]{tools:::Rd_expr_doi("10.1111/j.1365-3040.2007.01710.x")}].

PhotoGEA documentation built on Aug. 25, 2025, 5:13 p.m.