Symboles	Description	Valeurs	Unités	Sources
λ	Wave length of radiation blue and red	430 - 460 645 - 665	nm nm	Standard
h	Planck number	6.626 × 10⁻³⁴	m²∙kg∙S⁻¹
C	light speed	3 × 10⁸	m∙S⁻¹
$N$	Avogadro number	6.02 × 10²³	mol⁻¹
R	Constant of the perfect gas	8.31	J∙mol⁻¹∙K⁻¹
$V_{e a u}$	Molar volume of water	18 × 10⁻³	l∙mol⁻¹
$ρ$	Density of water in the xylem	10³	kg∙m⁻³
g	Acceleration of gravity	9.81	m∙S⁻²
r	Radius of the root	5 × 10⁻⁴	m	[8]
$k_{x}$	Axial conductivity of the root	10⁻⁹	m⁴∙Pa⁻¹∙S⁻¹
$k_{r}$	Radial conductivity of the root	2.5 × 10⁻⁷	m∙Pa⁻¹∙S⁻¹