Figure 3.

Calculated leaf sap osmolality at zero turgor and measured leaf sap osmolality at midafternoon in relation to phloem loading type. Leaf sap osmolality at zero turgor (C₀) was calculated using the equation ψ_s = –C₀RT, where ψ_s is osmotic potential, which was assumed to be equal to midafternoon leaf water potential at zero turgor, R is a universal gas constant (0.008314 L MPa⁻¹ K mol⁻¹), and T is the absolute temperature (K) at which leaf water potential was measured. Osmolality of the expressed sap from frozen leaf samples taken at midafternoon was measured with a freezing-point osmometer. Apo, Apoplastic loading; PT, polymer trapping; Pas, passive loading; s, Suc; sa, sugar alcohols. Values are means ± se (n = 4–9 species). Different letters above the bars of the same dependent variable indicate significant differences using Duncan’s multiple range test at P < 0.05 after ANOVA.