Determination of plant water use efficiency (WUE)
Intrinsic WUE (iWUE –A /g s ratio) (µmol CO2mmol-1 H2O) was estimated from steady
state values of A and g s under 1000 µmol
photons m-2 s-1 and 400 ppm
CO2 from A -PAR curves and stomatal opening
kinetics (described below). The data from WPT and biomass were used to
estimate season-long WUE (slWUE - ratio between the
amount of accumulated biomass per unit of water transpired) and yield
WUE (yWUE - ratio between the yield of the harvestable
organ (leaves) to water transpired over time) (Bacon 2004). For the
determination of both yWUE (g DW leaves
kg-1 H2O transpired) andslWUE (g DW kg-1 H2O
transpired), we used LA data to estimate the leaf and total biomass DW
of the beginning of the experiment by linear regression with accuracy of
R2 > 0.82 for leaves and
R2 > 0.95 for total biomass (Figure S1).