Low esk1 root hydraulic conductivity is mainly explained by a reduction in tracheary element diameter.

The 4 to 5 larger xylem vessels of 6 week-old plants of esk1 mutant alleles and wild type (wt) sections were analyzed for the maximal circular radius. The maximal conductivity (g) of the vessels was calculated according to Poiseuille's law.R = (8.η)/(π.r4) where g = 1/R (m2/s/MPa), η is the water viscosity coefficient (1E−9 MPa/s) and r is the maximal radius (µm).Max conductivity: maximal hydraulic conductivity calculated.Mean radius: mean of all radius measured (µm).Max radius: maximal radius measured (µm).