Pressure-volume curves and target water potential
Pressure-volume curves were generated for each species to estimate the
turgor loss point and select the initial leaf water potential (Ψ) value
for all FWU experiments. This target Ψ value corresponded to 70% of the
turgor loss point. We followed the bench drying technique (Hinckley et
al. 1980) using six randomly selected leaves per species. Briefly,
branches were cut underwater, placed in plastic bags to prevent
transpiration, and allowed to fully rehydrate. Leaves were then detached
from branches, weighed, and placed on a bench to desiccate at room
conditions (relative humidity, RH, ~30% and temperature
~22 ºC). Each leaf was re-weighed, and its Ψ was
measured with a pressure chamber during the drying period. The procedure
was halted when 10 to 15% of the initial leaf mass was lost. Leaves
were oven-dried at 80 ºC for three days to calculate their relative
water content (RWC) as RWC = (fresh weight–dry weight, DW)/(turgid
weight–DW). The turgor loss point was estimated from the
pressure-volume curves.