Table 1.

Nomenclature.

parameter	symbol	value and/or unit
length	x	m
viscosity		Pa s
membrane permeability		m s−1 Pa−1
length of leaf	,	m
length of stem	,	m
length of root		m
radius of phloem tube	r	m
optimal radius		m
water flow through tube wall	J	m s−1
pressure	p	Pa
osmotic flow velocity scale	U	m s−1
Münch number	Mü	dimensionless
leaf to stem length ratio		dimensionless
dimensionless sugar concentration gradient in root		dimensionless
volume flux	Q	m3 s−1
gas constant	R	m3 Pa K−1 mol−1
temperature	T	K
wall resistance		Pa m−3 s
tube resistance		Pa m−3 s
velocity	u	m s−1
dimensionless velocity	v	dimensionless
dimensionless length		dimensionless
dimensionless concentration		dimensionless
height of channel	h	m
intensity of fluorescence	I	arb. units
time	t	s