Fit pressure–volume curves

Fit leaf pressure–volume curves to get the osmotic pressure at full turgor, the turgor loss point, and the water potential at turgor loss. See Plant hydraulics models.

Inputs

A file with relative water content (RWC, as a fraction or a percentage) and water potential (Psi (MPa), Psi, WP, and similar). A column named in bar, such as Psi (bar), is converted to MPa. Positive tension is made negative.

Steps

examples/pv.csv holds three leaves, with a Leaf column:

pk fit hydraulics examples/pv.csv --model pvcurve --group-by Leaf

--group-by Leaf fits each leaf separately. The result lists one fit per leaf under results. Each fit has the parameters πo, wtlp and ε, and under derived, the water potential at turgor loss, psi_tlp:

{ "file": "Leaf 1", "r2": 0.999985, "params": { "πo": 1.597251, "wtlp": 0.871015, "ε": 1.244022 }, "derived": { "psi_tlp": -1.83378 } }

For a table with one row per leaf:

pk fit hydraulics examples/pv.csv --model pvcurve --group-by Leaf --format csv

To fit every leaf as one curve, leave out --group-by.