Figure 1.

Comparison of observed K_ox (red bars; means ± se) with ranges of simulated K_ox values possible for wide variation in unknown parameters [simulated (low) to simulated (high); gray bars]. For three of the unknown parameters (Poiseuille radius of apoplastic bulk flow pathways [R_a], osmotic water permeability of cell membranes [P_m], and the ratio of cell wall thickness used in the simulation to values measured by light microscopy [ρ_ta]), the high and low K_ox simulations used default values plus or minus 50%, respectively. For the other three unknown parameters (BS Casparian strip, horizontal palisade contact fraction ratio of true palisade horizontal connectivity to the value from microscopy [ρ_fcph], and vertical temperature gradient [ΔT]), we used the upper or lower limits of possible values (0% or 100% of apoplastic transport was blocked by a Casparian strip; ρ_fcph = 0 or 1; and ΔT = 0 or 0.2°C). Default values for these parameters are given in Table III.