Effect of FC and ABA on leaf rehydration via the adaxial surface
To evaluate the potential effects of FC and ABA treatments on water uptake and leaf rehydration not associated with changes in stomatal aperture, a preliminary experiment aiming to analyze FWU via only the adaxial, stomata-free surface was conducted with P. dulcisleaves. The abaxial surfaces and margins of fully rehydrated leaves supplied either with FC, ABA or water (six leaves per treatment) were covered with paraffin wax, and their cut-end petioles sealed. Leaf mass was recorded before and after wax application, as well as before treatment application. Leaves were allowed to dehydrate until reaching the mass associated with the target Ψ and placed in a ‘fog chamber’ (see below). After 100-120 min of fog exposure, leaves were taken out of the chamber and weighed after their surface was dried with pulses of dry air. A second set of leaves of each treatment (three leaves per treatment) was fully covered with wax, i.e. both their adaxial and abaxial surface, and placed in the chamber. After 100-120 min, the mass of the leaves from this second set remained the same which confirms that wax application was effective in sealing the surface. After the rehydration experiment, leaves were scanned and their area was calculated with ImageJ (v.1.45s National Institutes of Health, Bethesda, MD, USA). The amount of water absorbed via the adaxial leaf surface was calculated as the increment in mass following fog application per projected leaf surface area; the treatment effect was assessed by ANOVA in R.