Summary of the article:

Plant Water Supply
- The water supply from soil to leaves is modeled using Darcy's law for porous media flow.
- The conductance of each flow segment (soil-to-root, root-to-stem, stem-to-leaf) decreases as water potential decreases, captured by a sigmoidal vulnerability curve.

Stem-to-Leaf
- There are two stem-to-leaf flows in parallel: from stem to sunlit leaves and from stem to shaded leaves.
- Stem-to-leaf conductance is the maximum conductance multiplied by the percent of maximum conductance based on the vulnerability curve.
- The water flux depends on the leaf area index, stem water potential, and leaf water potential.

Root-to-Stem
- The root-to-stem flux represents the flow from the root collar to the upper branches.
- Root-to-stem conductance is the maximum conductance divided by the vegetation height, multiplied by the percent of maximum conductance.
- The flux depends on the stem area index, root water potential, stem water potential, and gravitational potential.

Soil-to-Root
- There are multiple soil-to-root fluxes operating in parallel, one for each root-containing soil layer.
- The soil-to-root conductance is the harmonic mean of the soil conductivity and root tissue conductance.
- The root tissue conductance is the maximum conductance divided by the root path length, multiplied by the percent of maximum conductance.
- The flux depends on the root area index, soil water potential, root water potential, and gravitational potential.