Table 1. Model Parameters.

	Parameter	Unit	Description	Acceptable range		Default
				Max.	Min.
BOR	$ϵ{}_B$	-	Time constant for transporter regulation	-	-	1
	$\alpha {}_B$	μm s-2	Production rate of transporter activity	$4.9\times {10}^2$	$3.7\times {10}^{-9}$	$2.0\times {10}^{-1}$
	$\xi {}_B$	s-1	Basal degradation rate		$1.6\times {10}^{-6}$	$7.6\times {10}^{-2}$
	$k_B$	μM	Boron concentration for half-maximum in Hill’s function	1000	1	600
	$d_B$	-	Amplitude of increased degradation rate by boron	100	0	50
	$n_B$	-	Hill’s coefficient	-	-	2
	$c_B$	μM	Boron concentration at which the flux reaches its half-maximum value	$\mathrm{\infty }$	500	1000
NIP	$ϵ{}_N$	-	Time constant for transporter regulation	-	-	1
	$\alpha {}_N$	μm s-2	Production rate of transporter activity	$4.9\times {10}^2$	$3.7\times {10}^{-9}$	$2.0\times {10}^{-1}$
	$\xi {}_N$	s-1	Basal degradation rate		$1.6\times {10}^{-6}$	$7.6\times {10}^{-2}$
	$k_N$	μM	Boron concentration for half-maximum in Hill’s function	1000	1	20
	$n_N$	-	Hill’s coefficient	-	-	2
Cell size	$lc$	μm	Cell width	20	5	10
	$lw$	μm	Cell wall width	2	0.2	0.5
	$hc$	μm	Cell height	150	5	20
Other	$p$	μm s-1	Membrane background permeability of boron	$8\times {10}^{-2}$	$2.3\times {10}^{-3}$	$3\times {10}^{-2}$
	$a$	μm s-1	Xylem loading rate (in the last cell)	500	0	0.5
	$c_0$	μm	Boron concentration in medium	5000	0	300