Coefficients for the von Caemmerer (2021) steady-state C4 photosynthesis model. More...

#include <PhotosynthesisModel.h>

Public Member Functions
void	setVpmax (float Vpmax)
	Set Vpmax (maximum PEPC activity) with no temperature response.

void	setVpmax (float Vpmax_at_25_C, float rate_of_increase_dHa)
	Set Vpmax with a monotonically increasing Arrhenius response.

void	setVpmax (float Vpmax_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C)
	Set Vpmax with a peaked Arrhenius response (optimum, default dHd).

void	setVpmax (float Vpmax_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C, float rate_of_decrease_dHd)
	Set Vpmax with a peaked Arrhenius response (optimum + explicit rate of decrease).

void	setVcmax (float Vcmax)
	Set Vcmax (maximum Rubisco activity) with no temperature response.

void	setVcmax (float Vcmax_at_25_C, float rate_of_increase_dHa)
	Set Vcmax with a monotonically increasing Arrhenius response.

void	setVcmax (float Vcmax_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C)
	Set Vcmax with a peaked Arrhenius response (optimum, default dHd).

void	setVcmax (float Vcmax_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C, float rate_of_decrease_dHd)
	Set Vcmax with a peaked Arrhenius response (optimum + explicit rate of decrease).

void	setJmax (float Jmax)
	Set Jmax (maximum linear electron transport rate) with no temperature response.

void	setJmax (float Jmax_at_25_C, float rate_of_increase_dHa)
	Set Jmax with a monotonically increasing Arrhenius response.

void	setJmax (float Jmax_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C)
	Set Jmax with a peaked Arrhenius response.

void	setJmax (float Jmax_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C, float rate_of_decrease_dHd)
	Set Jmax with a peaked Arrhenius response with explicit rate of decrease.

void	setRd (float Rd)
	Set Rd (leaf mitochondrial respiration) with no temperature response.

void	setRd (float Rd_at_25_C, float rate_of_increase_dHa)
	Set Rd with a monotonically increasing Arrhenius response.

void	setRd (float Rd_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C)
	Set Rd with a peaked Arrhenius response.

void	setRd (float Rd_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C, float rate_of_decrease_dHd)
	Set Rd with a peaked Arrhenius response with explicit rate of decrease.

void	setMesophyllConductance_gm (float gm)
	Set mesophyll conductance gm (mol CO2 / m^2 / s / bar) with no temperature response.

void	setMesophyllConductance_gm (float gm_at_25_C, float rate_of_increase_dHa)
	Set gm with a monotonically increasing Arrhenius response.

void	setMesophyllConductance_gm (float gm_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C)
	Set gm with a peaked Arrhenius response.

void	setMesophyllConductance_gm (float gm_at_25_C, float rate_of_increase_dHa, float optimum_temperature_in_C, float rate_of_decrease_dHd)
	Set gm with a peaked Arrhenius response with explicit rate of decrease.

PhotosyntheticTemperatureResponseParameters	getVpmaxTempResponse () const

PhotosyntheticTemperatureResponseParameters	getVcmaxTempResponse () const

PhotosyntheticTemperatureResponseParameters	getJmaxTempResponse () const

PhotosyntheticTemperatureResponseParameters	getRdTempResponse () const

PhotosyntheticTemperatureResponseParameters	getMesophyllConductance_gmTempResponse () const

Data Fields
float	Kc_25 = 1210.f
	Michaelis constant of Rubisco for CO2 at 25 °C (μbar)

float	Ko_25 = 292000.f
	Michaelis constant of Rubisco for O2 at 25 °C (μbar = 292 mbar)

float	Kp_25 = 82.f
	Michaelis constant of PEPC for CO2 at 25 °C (μbar)

float	gamma_star_25 = 3.81679e-4f
	0.5 / S_Rubisco at 25 °C (dimensionless)

float	Om_25 = 210000.f
	Mesophyll O2 partial pressure at 25 °C (μbar = 210 mbar, ambient)

float	dH_Kc = 64.2f
	Activation energy for Kc (kJ/mol)

float	dH_Ko = 10.5f
	Activation energy for Ko (kJ/mol)

float	dH_Kp = 38.3f
	Activation energy for Kp (kJ/mol)

float	dH_gamma_star = 31.1f
	Activation energy for γ* (kJ/mol; positive — γ* increases with T because S_c/o decreases with T; see block comment above)

float	dH_Om = 0.f
	Activation energy for Om (kJ/mol; ambient O2, assumed T-independent)

float	alpha_psII_fraction = 0.f
	α — fraction of PSII activity in the bundle sheath (0 for NADP-ME; range [0,1])

float	x_etr_partition = 0.4f
	x — fraction of linear electron-transport rate partitioned to the mesophyll

float	Vpr = 80.f
	PEP regeneration rate cap (μmol/m²/s)

float	Rm_frac = 0.5f
	R_m = Rm_frac · R_d (mesophyll mitochondrial respiration as a fraction of total)

float	fcyc = 0.45f
	Fraction of linear electron flow that is cyclic (Woodford et al. 2025 Table 1; updated from 0.3 in vC2021 to reflect NDH dominance — Ermakova 2024, Yin & Struik 2012)

float	gbs = 0.003f
	Bundle-sheath conductance to CO2 (mol/m²/s/bar), constant with temperature.

float	ao = 0.047f
	O2/CO2 solubility-diffusivity ratio (a_o in Eq. 15)

float	absorptance = 0.85f
	Leaf PAR absorptance (fraction of incident PAR absorbed)

float	f_spectral = 0.15f
	Spectral-quality correction to absorbed PAR (Eq. 35)

float	theta_etr = 0.7f
	Curvature of the J ~ I2 non-rectangular hyperbola (Eq. 34)

float	h_protons = 4.f
	Protons required per ATP synthesized (Eq. 31)

float	H_J = 3.f
	Protons per electron for linear electron flow (H⁺/e⁻; Woodford et al. 2025 Table 1)

float	H_Jcyc = 3.4f
	Protons per electron for cyclic electron flow (H⁺/e⁻; Woodford et al. 2025 Table 1, reflecting NDH dominance)

Friends
class	PhotosynthesisModel

Detailed Description

Coefficients for the von Caemmerer (2021) steady-state C4 photosynthesis model.

Parameters are divided into three groups: 1) Temperature-responsive enzyme/electron-transport rates (Vpmax, Vcmax, Jmax, Rd, gm) — each has the same four setter overloads as the C3 Farquhar model (constant / Arrhenius / peaked / peaked+dHd). 2) Rubisco + PEPC kinetic constants (Kc, Ko, Kp, γ*) — stored as public fields and evaluated with a simple Arrhenius response at the 25 °C reference, mirroring the C3 Farquhar treatment of Kc/Ko. 3) User-tunable scalar parameters with paper defaults (α, x, Vpr, Rm_frac, fcyc, gbs, ao, Om, …). Defaults for Setaria viridis follow Table 1 of von Caemmerer, S. (2021) "Updating the steady-state model of C4 photosynthesis", Journal of Experimental Botany 72:6003–6017.

Definition at line 554 of file PhotosynthesisModel.h.

Constructor & Destructor Documentation

◆ C4ModelCoefficients()

C4ModelCoefficients::C4ModelCoefficients ( )

inline

Definition at line 556 of file PhotosynthesisModel.h.

Member Function Documentation

◆ getJmaxTempResponse()

PhotosyntheticTemperatureResponseParameters C4ModelCoefficients::getJmaxTempResponse ( ) const

inline

Definition at line 658 of file PhotosynthesisModel.h.

◆ getMesophyllConductance_gmTempResponse()

PhotosyntheticTemperatureResponseParameters C4ModelCoefficients::getMesophyllConductance_gmTempResponse ( ) const

inline

Definition at line 660 of file PhotosynthesisModel.h.

◆ getRdTempResponse()

PhotosyntheticTemperatureResponseParameters C4ModelCoefficients::getRdTempResponse ( ) const

inline

Definition at line 659 of file PhotosynthesisModel.h.

◆ getVcmaxTempResponse()

PhotosyntheticTemperatureResponseParameters C4ModelCoefficients::getVcmaxTempResponse ( ) const

inline

Definition at line 657 of file PhotosynthesisModel.h.

◆ getVpmaxTempResponse()

PhotosyntheticTemperatureResponseParameters C4ModelCoefficients::getVpmaxTempResponse ( ) const

inline

Definition at line 656 of file PhotosynthesisModel.h.

◆ setJmax() [1/4]

void C4ModelCoefficients::setJmax ( float Jmax )

inline

Set Jmax (maximum linear electron transport rate) with no temperature response.

Definition at line 605 of file PhotosynthesisModel.h.

◆ setJmax() [2/4]

void C4ModelCoefficients::setJmax	(	float	Jmax_at_25_C,
		float	rate_of_increase_dHa
	)

inline

Set Jmax with a monotonically increasing Arrhenius response.

Definition at line 609 of file PhotosynthesisModel.h.

◆ setJmax() [3/4]

void C4ModelCoefficients::setJmax	(	float	Jmax_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C
	)

inline

Set Jmax with a peaked Arrhenius response.

Definition at line 613 of file PhotosynthesisModel.h.

◆ setJmax() [4/4]

void C4ModelCoefficients::setJmax	(	float	Jmax_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C,
		float	rate_of_decrease_dHd
	)

inline

Set Jmax with a peaked Arrhenius response with explicit rate of decrease.

Definition at line 617 of file PhotosynthesisModel.h.

◆ setMesophyllConductance_gm() [1/4]

void C4ModelCoefficients::setMesophyllConductance_gm ( float gm )

inline

Set mesophyll conductance gm (mol CO2 / m^2 / s / bar) with no temperature response.

Definition at line 639 of file PhotosynthesisModel.h.

◆ setMesophyllConductance_gm() [2/4]

void C4ModelCoefficients::setMesophyllConductance_gm	(	float	gm_at_25_C,
		float	rate_of_increase_dHa
	)

inline

Set gm with a monotonically increasing Arrhenius response.

Definition at line 643 of file PhotosynthesisModel.h.

◆ setMesophyllConductance_gm() [3/4]

void C4ModelCoefficients::setMesophyllConductance_gm	(	float	gm_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C
	)

inline

Set gm with a peaked Arrhenius response.

Definition at line 647 of file PhotosynthesisModel.h.

◆ setMesophyllConductance_gm() [4/4]

void C4ModelCoefficients::setMesophyllConductance_gm	(	float	gm_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C,
		float	rate_of_decrease_dHd
	)

inline

Set gm with a peaked Arrhenius response with explicit rate of decrease.

Definition at line 651 of file PhotosynthesisModel.h.

◆ setRd() [1/4]

void C4ModelCoefficients::setRd ( float Rd )

inline

Set Rd (leaf mitochondrial respiration) with no temperature response.

Definition at line 622 of file PhotosynthesisModel.h.

◆ setRd() [2/4]

void C4ModelCoefficients::setRd	(	float	Rd_at_25_C,
		float	rate_of_increase_dHa
	)

inline

Set Rd with a monotonically increasing Arrhenius response.

Definition at line 626 of file PhotosynthesisModel.h.

◆ setRd() [3/4]

void C4ModelCoefficients::setRd	(	float	Rd_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C
	)

inline

Set Rd with a peaked Arrhenius response.

Definition at line 630 of file PhotosynthesisModel.h.

◆ setRd() [4/4]

void C4ModelCoefficients::setRd	(	float	Rd_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C,
		float	rate_of_decrease_dHd
	)

inline

Set Rd with a peaked Arrhenius response with explicit rate of decrease.

Definition at line 634 of file PhotosynthesisModel.h.

◆ setVcmax() [1/4]

void C4ModelCoefficients::setVcmax ( float Vcmax )

inline

Set Vcmax (maximum Rubisco activity) with no temperature response.

Definition at line 588 of file PhotosynthesisModel.h.

◆ setVcmax() [2/4]

void C4ModelCoefficients::setVcmax	(	float	Vcmax_at_25_C,
		float	rate_of_increase_dHa
	)

inline

Set Vcmax with a monotonically increasing Arrhenius response.

Definition at line 592 of file PhotosynthesisModel.h.

◆ setVcmax() [3/4]

void C4ModelCoefficients::setVcmax	(	float	Vcmax_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C
	)

inline

Set Vcmax with a peaked Arrhenius response (optimum, default dHd).

Definition at line 596 of file PhotosynthesisModel.h.

◆ setVcmax() [4/4]

void C4ModelCoefficients::setVcmax	(	float	Vcmax_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C,
		float	rate_of_decrease_dHd
	)

inline

Set Vcmax with a peaked Arrhenius response (optimum + explicit rate of decrease).

Definition at line 600 of file PhotosynthesisModel.h.

◆ setVpmax() [1/4]

void C4ModelCoefficients::setVpmax ( float Vpmax )

inline

Set Vpmax (maximum PEPC activity) with no temperature response.

Definition at line 571 of file PhotosynthesisModel.h.

◆ setVpmax() [2/4]

void C4ModelCoefficients::setVpmax	(	float	Vpmax_at_25_C,
		float	rate_of_increase_dHa
	)

inline

Set Vpmax with a monotonically increasing Arrhenius response.

Definition at line 575 of file PhotosynthesisModel.h.

◆ setVpmax() [3/4]

void C4ModelCoefficients::setVpmax	(	float	Vpmax_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C
	)

inline

Set Vpmax with a peaked Arrhenius response (optimum, default dHd).

Definition at line 579 of file PhotosynthesisModel.h.

◆ setVpmax() [4/4]

void C4ModelCoefficients::setVpmax	(	float	Vpmax_at_25_C,
		float	rate_of_increase_dHa,
		float	optimum_temperature_in_C,
		float	rate_of_decrease_dHd
	)

inline

Set Vpmax with a peaked Arrhenius response (optimum + explicit rate of decrease).

Definition at line 583 of file PhotosynthesisModel.h.

Friends And Related Symbol Documentation

◆ PhotosynthesisModel

friend class PhotosynthesisModel

friend

Definition at line 718 of file PhotosynthesisModel.h.

Field Documentation

◆ absorptance

float C4ModelCoefficients::absorptance = 0.85f

Leaf PAR absorptance (fraction of incident PAR absorbed)

Definition at line 697 of file PhotosynthesisModel.h.

◆ alpha_psII_fraction

float C4ModelCoefficients::alpha_psII_fraction = 0.f

α — fraction of PSII activity in the bundle sheath (0 for NADP-ME; range [0,1])

Definition at line 690 of file PhotosynthesisModel.h.

◆ ao

float C4ModelCoefficients::ao = 0.047f

O2/CO2 solubility-diffusivity ratio (a_o in Eq. 15)

Definition at line 696 of file PhotosynthesisModel.h.

◆ dH_gamma_star

float C4ModelCoefficients::dH_gamma_star = 31.1f

Activation energy for γ* (kJ/mol; positive — γ* increases with T because S_c/o decreases with T; see block comment above)

Definition at line 685 of file PhotosynthesisModel.h.

◆ dH_Kc

float C4ModelCoefficients::dH_Kc = 64.2f

Activation energy for Kc (kJ/mol)

Definition at line 672 of file PhotosynthesisModel.h.

◆ dH_Ko

float C4ModelCoefficients::dH_Ko = 10.5f

Activation energy for Ko (kJ/mol)

Definition at line 673 of file PhotosynthesisModel.h.

◆ dH_Kp

float C4ModelCoefficients::dH_Kp = 38.3f

Activation energy for Kp (kJ/mol)

Definition at line 674 of file PhotosynthesisModel.h.

◆ dH_Om

float C4ModelCoefficients::dH_Om = 0.f

Activation energy for Om (kJ/mol; ambient O2, assumed T-independent)

Definition at line 686 of file PhotosynthesisModel.h.

◆ f_spectral

float C4ModelCoefficients::f_spectral = 0.15f

Spectral-quality correction to absorbed PAR (Eq. 35)

Definition at line 698 of file PhotosynthesisModel.h.

◆ fcyc

float C4ModelCoefficients::fcyc = 0.45f

Fraction of linear electron flow that is cyclic (Woodford et al. 2025 Table 1; updated from 0.3 in vC2021 to reflect NDH dominance — Ermakova 2024, Yin & Struik 2012)

Definition at line 694 of file PhotosynthesisModel.h.

◆ gamma_star_25

float C4ModelCoefficients::gamma_star_25 = 3.81679e-4f

0.5 / S_Rubisco at 25 °C (dimensionless)

Definition at line 669 of file PhotosynthesisModel.h.

◆ gbs

float C4ModelCoefficients::gbs = 0.003f

Bundle-sheath conductance to CO2 (mol/m²/s/bar), constant with temperature.

Definition at line 695 of file PhotosynthesisModel.h.

◆ H_J

float C4ModelCoefficients::H_J = 3.f

Protons per electron for linear electron flow (H⁺/e⁻; Woodford et al. 2025 Table 1)

Definition at line 708 of file PhotosynthesisModel.h.

◆ H_Jcyc

float C4ModelCoefficients::H_Jcyc = 3.4f

Protons per electron for cyclic electron flow (H⁺/e⁻; Woodford et al. 2025 Table 1, reflecting NDH dominance)

Definition at line 709 of file PhotosynthesisModel.h.

◆ h_protons

float C4ModelCoefficients::h_protons = 4.f

Protons required per ATP synthesized (Eq. 31)

Definition at line 700 of file PhotosynthesisModel.h.

◆ Kc_25

float C4ModelCoefficients::Kc_25 = 1210.f

Michaelis constant of Rubisco for CO2 at 25 °C (μbar)

Definition at line 666 of file PhotosynthesisModel.h.

◆ Ko_25

float C4ModelCoefficients::Ko_25 = 292000.f

Michaelis constant of Rubisco for O2 at 25 °C (μbar = 292 mbar)

Definition at line 667 of file PhotosynthesisModel.h.

◆ Kp_25

float C4ModelCoefficients::Kp_25 = 82.f

Michaelis constant of PEPC for CO2 at 25 °C (μbar)

Definition at line 668 of file PhotosynthesisModel.h.

◆ Om_25

float C4ModelCoefficients::Om_25 = 210000.f

Mesophyll O2 partial pressure at 25 °C (μbar = 210 mbar, ambient)

Definition at line 670 of file PhotosynthesisModel.h.

◆ Rm_frac

float C4ModelCoefficients::Rm_frac = 0.5f

R_m = Rm_frac · R_d (mesophyll mitochondrial respiration as a fraction of total)

Definition at line 693 of file PhotosynthesisModel.h.

◆ theta_etr

float C4ModelCoefficients::theta_etr = 0.7f

Curvature of the J ~ I2 non-rectangular hyperbola (Eq. 34)

Definition at line 699 of file PhotosynthesisModel.h.

◆ Vpr

float C4ModelCoefficients::Vpr = 80.f

PEP regeneration rate cap (μmol/m²/s)

Definition at line 692 of file PhotosynthesisModel.h.

◆ x_etr_partition

float C4ModelCoefficients::x_etr_partition = 0.4f

x — fraction of linear electron-transport rate partitioned to the mesophyll

Definition at line 691 of file PhotosynthesisModel.h.

The documentation for this struct was generated from the following file:

plugins/photosynthesis/include/PhotosynthesisModel.h

	1.3.82

Public Member Functions

Data Fields

Friends

Detailed Description

Constructor & Destructor Documentation

◆ C4ModelCoefficients()

Member Function Documentation

◆ getJmaxTempResponse()

◆ getMesophyllConductance_gmTempResponse()

◆ getRdTempResponse()

◆ getVcmaxTempResponse()

◆ getVpmaxTempResponse()

◆ setJmax() [1/4]

◆ setJmax() [2/4]

◆ setJmax() [3/4]

◆ setJmax() [4/4]

◆ setMesophyllConductance_gm() [1/4]

◆ setMesophyllConductance_gm() [2/4]

◆ setMesophyllConductance_gm() [3/4]

◆ setMesophyllConductance_gm() [4/4]

◆ setRd() [1/4]

◆ setRd() [2/4]

◆ setRd() [3/4]

◆ setRd() [4/4]

◆ setVcmax() [1/4]

◆ setVcmax() [2/4]

◆ setVcmax() [3/4]

◆ setVcmax() [4/4]

◆ setVpmax() [1/4]

◆ setVpmax() [2/4]

◆ setVpmax() [3/4]

◆ setVpmax() [4/4]

Friends And Related Symbol Documentation

◆ PhotosynthesisModel

Field Documentation

◆ absorptance

◆ alpha_psII_fraction

◆ ao

◆ dH_gamma_star

◆ dH_Kc

◆ dH_Ko

◆ dH_Kp

◆ dH_Om

◆ f_spectral

◆ fcyc

◆ gamma_star_25

◆ gbs

◆ H_J

◆ H_Jcyc

◆ h_protons

◆ Kc_25

◆ Ko_25

◆ Kp_25

◆ Om_25

◆ Rm_frac

◆ theta_etr

◆ Vpr

◆ x_etr_partition