Isotope discrimination against¹³C (Δ¹³C) of water-soluble extracts vs. leaf mass per area (LMA) (a), g_mes (b) and instantaneous water use efficiency (WUE_i = A / g_s) (c) per season (winter, black; summer, white). Symbols represent single measurements of: control (C; •, ◦); winter resprouts, (RW; ▲, ∆); summer resprouts, (RS; ∇). Asterisks indicate statistically significant correlations (* p ≤ 0.05).