plantecophys (version 0.6-3)

Photosyn: Coupled leaf gas exchange model

Description

A coupled photosynthesis - stomatal conductance model, based on the Farquhar model of photosynthesis, and a Ball-Berry type model of stomatatal conductance. Includes options for temperature sensitivity of photosynthetic parameters, dark respiration (optionally calculated from leaf temperature), and mesophyll conductance.

Usage

Photosyn(VPD = 1.5, Ca = 400, PPFD = 1500, Tleaf = 25, Patm = 101,
  RH = NULL, gsmodel = c("BBOpti", "BBLeuning", "BallBerry"), g1 = 4,
  g0 = 0, gk = 0.5, vpdmin = 0.5, D0 = 5, GS = NULL, alpha = 0.24,
  theta = 0.85, Jmax = 100, Vcmax = 50, gmeso = NULL, Rd0 = 0.92,
  Q10 = 1.92, Rd = NULL, TrefR = 25, Rdayfrac = 1, EaV = 82620.87,
  EdVC = 0, delsC = 645.1013, EaJ = 39676.89, EdVJ = 2e+05,
  delsJ = 641.3615, GammaStar = NULL, Km = NULL, Ci = NULL,
  Tcorrect = TRUE, returnParsOnly = FALSE, whichA = c("Ah", "Amin", "Ac",
  "Aj"))

Aci(Ci, ...)

Arguments

VPD

Vapour pressure deficit (kPa)

Ca

Atmospheric CO2 concentration (ppm)

PPFD

Photosynthetic photon flux density ('PAR') (mu mol m-2 s-1)

Tleaf

Leaf temperature (degrees C)

Patm

Atmospheric pressure (kPa)

RH

Relative humidity (in %)

gsmodel

One of BBOpti (Medlyn et al. 2011), BBLeuning (Leuning 1995), or BallBerry (Ball et al. 1987)

g0,g1

Parameters of Ball-Berry type stomatal conductance models.

gk

Optional, exponent of VPD in gs model (Duursma et al. 2013)

vpdmin

Below vpdmin, VPD=vpdmin, to avoid very high gs.

D0

Parameter for the BBLeuning stomatal conductance model.

GS

Optionally, stomatal conductance (to H2O). If provided, Photosyn calculates Ci and photosynthesis. See Details.

alpha

Quantum yield of electron transport (mol mol-1)

theta

Shape of light response curve.

Jmax

Maximum rate of electron transport at 25 degrees C (mu mol m-2 s-1)

Vcmax

Maximum carboxylation rate at 25 degrees C (mu mol m-2 s-1)

gmeso

Mesophyll conductance (mol m-2 s-1). If not NULL (the default), Vcmax and Jmax are chloroplastic rates.

Rd0

Dark respiration rata at reference temperature (TrefR)

Q10

Temperature sensitivity of Rd.

Rd

Dark respiration rate (mu mol m-2 s-1), optional (if not provided, calculated from Tleaf, Rd0, Q10 and TrefR)

TrefR

Reference temperature for Rd (Celcius).

Rdayfrac

Ratio of Rd in the light vs. in the dark.

EaV,EdVC,delsC

Vcmax temperature response parameters

EaJ,EdVJ,delsJ

Jmax temperature response parameters

Km,GammaStar

Optionally, provide Michaelis-Menten coefficient for Farquhar model, and Gammastar. If not provided, they are calculated with a built-in function of leaf temperature.

Ci

Optional, intercellular CO2 concentration (ppm). If not provided, calculated via gs model.

Tcorrect

If TRUE, corrects input Vcmax and Jmax for actual Tleaf (if FALSE, assumes the provided Vcmax and Jmax are at the Tleaf provided)

returnParsOnly

If TRUE, returns calculated Vcmax,Jmax,Km and GammaStar based on leaf temperature.

whichA

Which assimilation rate does gs respond to?

...

Further arguments passed to Photosyn

Value

• Returns a dataframe.

Details

The coupled photosynthesis - stomatal conductance model finds the intersection between the supply of CO2 by diffusion, and the demand for CO2 by photosynthesis. See Farquhar and Sharkey (1982) for basic description of this type of model. The model of Farquhar et al. (1980) is used to estimate the dependence of photosynthesis rate on Ci. The temperature response of photosynthetic parameters, including Vcmax, Jmax, Gammastar, and Km follow Medlyn et al. 2002. At the moment, two stomatal conductance models are implemented, both are Ball-Berry type models. The 'BBOpti' model is a slightly more general form of the model of Medlyn et al. 2011 (see Duursma et al. 2013). It is given by (in notation of the parameters and output variables of Photosyn), $$GS = G0 + 1.6*(1 + G1/D^GK)*ALEAF/CA$$ where GK = 0.5 if stomata behave optimally (cf. Medlyn et al. 2011). The 'BBLeuning' model is that of Leuning (1995). It is given by, $$GS = G0 + g1*ALEAF/(Ca * (1 + VPD/D0))$$ Note that this model also uses the g1 parameter, but it needs to be set to a much higher value to be comparable in magnitude to the BBOpti model. The 'BallBerry' model is that of Ball et al. (1987). It is given by, $$GS = G0 + g1*RH*ALEAF/Ca$$ Where RH is relative humidity. For the full numerical solution to the Cowan-Farquhar optimization, use the FARAO function. If the mesophyll conductance is provided, it is assumed that Vcmax and Jmax are the chloroplastic rates, and leaf photosynthesis is calculated following Ethier and Livingston (2004). If Ci is provided as an input, this function calculates an A-Ci curve. Otherwise, Ci is calculated from the intersection between the 'supply' and 'demand', where 'demand' is given by the Farquhar model of photosynthesis (A=f(Ci)), and supply by the stomatal conductance. The latter is, by default, estimated using the stomatal conductance model of Medlyn et al. (2011), but two other models are provided as well (Ball-Berry and Leuning, see gsmodel argument). Otherwise, stomatal conductance may be directly provided via the GS argument. Note that the function Aci is provided as a shorthand for Photosyn(Ci=x). By default, the Photosyn function returns the hyperbolic minimum of Vcmax and Jmax-limited photosynthetic rates. This is to avoid the discontinuity at the transition between the two rates. Both Ac and Aj are also returned should they be needed. Note that those rates are output as gross photosynthetic rates (leaf respiration has to be subtracted to give net leaf photosynthesis).

References

Duursma, R.A., Payton, P., Bange, M.P., Broughton, K.J., Smith, R.A., Medlyn, B.E., Tissue, D. T., 2013, Near-optimal response of instantaneous transpiration efficiency to vapour pressure deficit, temperature and [CO2] in cotton (Gossypium hirsutum L.). Agricultural and Forest Meteorology 168 : 168 - 176. Ethier, G. and N. Livingston. 2004. On the need to incorporate sensitivity to CO2 transfer conductance into the Farquhar von Caemmerer Berry leaf photosynthesis model. Plant, Cell & Environment. 27:137-153. Farquhar, G.D., S. Caemmerer and J.A. Berry. 1980. A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species. Planta. 149:78-90. Farquhar, G. D., & Sharkey, T. D. (1982). Stomatal conductance and photosynthesis. Annual review of plant physiology, 33(1), 317-345. Leuning, R. 1995. A critical-appraisal of a combined stomatal-photosynthesis model for C-3 plants. Plant Cell and Environment. 18:339-355. Medlyn, B.E., E. Dreyer, D. Ellsworth, M. Forstreuter, P.C. Harley, M.U.F. Kirschbaum, X. Le Roux, P. Montpied, J. Strassemeyer, A. Walcroft, K. Wang and D. Loustau. 2002. Temperature response of parameters of a biochemically based model of photosynthesis. II. A review of experimental data. Plant Cell and Environment. 25:1167-1179. Medlyn, B.E., R.A. Duursma, D. Eamus, D.S. Ellsworth, I.C. Prentice, C.V.M. Barton, K.Y. Crous, P. De Angelis, M. Freeman and L. Wingate. 2011. Reconciling the optimal and empirical approaches to modelling stomatal conductance. Global Change Biology. 17:2134-2144.

See Also

FARAO, fitaci, AciC4

Examples

# Run the coupled leaf gas exchange model, set only a couple of parameters
Photosyn(VPD=2, g1=4, Ca=500)

# It is easy to set multiple values for inputs (and these can be mixed with single inputs);
r <- Photosyn(VPD=seq(0.5, 4, length=25), Vcmax=50, Jmax=100)
with(r, plot(VPD, ALEAF, type='l'))

# Set the mesophyll conductance
run1 <- Photosyn(PPFD=seq(50,1000,length=25), gmeso=0.15, Vcmax=40, Jmax=85)
with(run1, plot(PPFD, GS, type='l'))

# Run A-Ci curve only (provide Ci instead of calculating it).
arun1 <- Aci(Ci=seq(50, 1200, length=101), Vcmax=40, Jmax=85)
arun2 <- Aci(Ci=seq(50, 1200, length=101), Vcmax=30, Jmax=70)
with(arun1, plot(Ci, ALEAF, type='l'))
with(arun2, points(Ci, ALEAF, type='l', lty=5))

# Find the intersection between supply of CO2 and demand for CO2 (cf. Farquhar and Sharkey 1982).

# Set some parameters
gs <- 0.2  # stomatal conductance to H2O
Ca <- 400  # ambient CO2
gctogw <- 1.57  # conversion
gc <- gs / gctogw  # stomatal conductance to CO2

# Demand curve (Farquhar model)
p <- Aci(seq(60,500,length=101), Ca=400)

# Provide stomatal conductance as input, gives intersection point.
g <- Photosyn(GS=gs, Ca=Ca)

# Intersection point visualized
par(yaxs="i")
with(p, plot(Ci, ALEAF, type='l', ylim=c(0,max(ALEAF))))
with(g, points(Ci, ALEAF, pch=19, col="red"))
abline(gc * Ca, -gc, lty=5)

legend("topleft", c(expression("Demand:"~~A==f(C[i])),
                    expression("Supply:"~~A==g[c]*(C[a]-C[i])),
                    "Operating point"),
       lty=c(1,5,-1),pch=c(-1,-1,19),
       col=c("black","black","red"),
       bty='n', cex=0.9)