Effect of FC and ABA treatments – stomatal conductance of dehydrating leaves
For both species, treatments significantly affected gs(P <0.0001, Table 2 Supporting Information). The gs of P. dulcis and P. communis was higher for FC than for ABA and control leaves (Table 1, Figure 1). Very small negative values of gs recorded for P. dulcis ABA and control leaves were likely associated with transpiration rates below the detection limit of the photosynthesis system and not significantly different from 0, suggesting that stomata were mainly shut. The gs for the different treatments is consistent with values reported for plants growing in field conditions (Marsal and Girona 1997; Spinelli et al. 2016). For both species, values of gs indicate that treatments were effective in modifying stomatal aperture across the Ψ range where FWU was analyzed (Figure 1). The observed variation of gs with Ψ suggests that, despite the treatments, stomatal responses were still affected by Ψ. However, FC forced stomata to remain open even under significant stress. ABA treatment was also successful in both species reducing gs to near zero. The control treatment seemed to almost fully close stomata in P. dulcis but not in P. communis , providing the opportunity to test the contribution of partially shut stomata to FWU.