Table 1.

Energy balance parameters, environmental variables, and physical constants

Symbol	Description	Unit
Gas exchange
A	Net CO2 assimilation rate	µmol m–2 s–1
g sw	Stomatal conductance to water vapour	mol m–2 s–1
g bw	Boundary layer conductance to water vapour	mol m–2 s–1
g bh	Boundary layer conductance to heat transfer	m s–1
g tw	Total conductance to water vapour	mol m–2 s–1
E	Transpiration rate	kg m–2 s–1
VPD l	Leaf to air vapour pressure deficit	Pa
g 1, g2, g3	Steady-state targets for gsw for the dark/light/dark periods	mol m–2 s–1
ϕi, ϕd	Time lag for an increase (i) or a decrease (d) in gsw	s
τi, τd	Time constant for an increase (i) or a decrease (d) in gsw	s–1
S l	Slope of the linear variation of gsw during the light period	µmol m–2 s–2
Energy balance
T leaf	Leaf temperature	°C/°K
R n	Net radiation	W m–2
C	Sensible heat transfer	W m–2
λ	latent heat of evaporation of water	J kg–1
S	Net physical storage	W m–2
αl, αb, αw	Short-wave absorbance of the leaf (l), black reference (b), and white reference (w)
εl, εb, εw	Emissivity of the leaf (l), black reference (b), and white reference (w)
k	Amount of energy per unit area required to change the temperature of the material by 1 °K	J m–2 K–1
ρ, ρ*	Density of air and leaf tissue (*)	kg m–3
C s	Specific heat capacity of humid air	J kg–1 K–1
C p*	Leaf specific heat capacity	J kg–1 K–1
l*	Leaf thickness	m
Environment
I s	Incident shortwave radiations	W m–2
PPFD	Photosynthetic photon flux density	µmol m–2 s–1
RH	Air relative humidity
T air	Air temperature	°C/°K
P atm	Atmospheric pressure	Pa
e s, ea	Leaf internal (s) and air (a) vapour pressure	Pa
Constant
θ	Stefan–Boltzmann constant	W m–2 K–4
R	Gas constant	m3 Pa K−1 mol−1