Table II.

Calculating sieve tube-specific conductivity, k

Calculations of k for both species are made from mean values of each of the parameters below, following Equation 1. k relates turgor pressure drop, Δp, to translocation velocity, U, according to Δp = μUL/k, where μ is sap viscosity and L is translocation distance (Thompson, 2006). stderr, Standard error.

Variable (Eq. 1)Value ± stderr (N)
Arabidopsis Stem PhloemTobacco Petiole Phloem
r (μm)2.0 ± 0.1 (7)5.5 ± 0.2 (16)
l (μm)107 ± 7 (13)122 ± 13 (11)
rp (μm)0.26 ± 0.01 (7)a0.35 ± 0.01 (3)a
lp (μm)1.0 ± 0.1 (14)1.2 ± 0.1 (19)
Np52 ± 6 (7)a108 ± 8 (3)a
k (μm2)0.280.45
  • a These data were derived from images of aniline-blue stained callose (Fig. 6).