c4_temperature_param_vc {PhotoGEA} | R Documentation |
C4 temperature response parameters from von Caemmerer
Description
Temperature response parameters describing the temperature response of
important C4 photosynthetic parameters, intended to be passed to the
calculate_temperature_response
function.
Usage
c4_temperature_param_vc
Format
List with 10 named elements that each represent a variable whose temperature-dependent value can be calculated using either an Arrhenius or Gaussian 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 ofVcmax
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_norm
: The mesophyll conductance to CO2 diffusion normalized to its value at 25 degrees C. -
J_norm
: The electron transport rateJ
normalized to its value at 25 degrees C.
The J_norm
parameter is calculated using a Gaussian function and
hence its corresponding list element is itself a list with 4 named elements:
-
type
: the type of temperature response ('Gaussian'
) -
optimum_rate
: the largest value this parameter can take. -
t_opt
: the temperature where the optimum occurs indegrees C
. -
sigma
: the width of the Gaussian indegrees C
. -
units
: the units of the corresponding variable.
Each of the remaining elements is a list with 4 named elements:
-
type
: the type of temperature response ('Arrhenius'
) -
c
: the (dimensionless) Arrhenius scaling factor. -
Ea
: the activation energy inkJ / mol
. -
units
: the units of the corresponding variable.
Source
Some of these parameters (Vcmax
, Vpmax
, RL
, gmc
,
and J
) 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
,
and ao
) are not normalized because they are assumed to not vary
significantly between species.
Here, the Arrhenius scaling factors (c
; dimensionless) and activation
energy values (Ea
; kJ / mol) are obtained from von Caemmerer (2021). In
that publication, the overall scaling for each parameter is specified by its
value at 25 degrees C; the scaling factors are determined from this
information as described in the documentation for
calculate_temperature_response_arrhenius
.
The Gaussian parameters (t_opt
and sigma
) for J_norm
are also obtained from von Caemmerer (2021), assuming that J
and
Jmax
follow the same temperature response. The value of
optimum_rate
is chosen such that J_norm
is equal to 1 at a
temperature of 25 degrees C.
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].