Fig. 5.

The fractions of whole-lamina N in support biomass (eqn 4) vs. the fraction of dry mass in support within the lamina, i.e. mid-rib/(lamina with mid-rib) (A), the fraction of whole-leaf N in support biomass in relation to the fraction of support biomass within the leaf (B), and the relative difference in N percentage between lamina without mid-rib (N_L) and entire lamina N_LT (R^N_LT, eqn 5) in relation to the fraction of dry mass in support within lamina (C), and the relative difference [R^N_LW = (N_L – N_WL)/N_L] in N percentage between lamina without mid-rib and whole leaf (R^N_LW, eqn 6) (D). Data presentation and fitting for 122 species as in Fig. 3. All regressions are significant at P < 0·001. The arrow on panel C denotes an outlying observation for Leontodon taraxacoides that had a large fraction of biomass in support, but a relatively small difference in N percentage between mid-rib (2·72 ± 0·03 %) and the rest of the lamina (3·11 ± 0·13 %). The explained variance was improved by removing this outlying observation (r² = 0·77), but the slope and intercept of the regression equation were marginally modified (data not shown).