Fig. 10.
Diagrammatic representation of vein pattern formation in leaves of C3 and C4 Flaveria species. Leaf developmental stages relate formation of vein orders to leaf length and leaf plastochron index (LPI) for each species. The onset of vein orders (major and minor) occurs in leaves that are equivalent in length for the two species, and leaf expansion is relatively similar. Lateral lamina expansion occurs earlier in C4 Flaveria and at later stages in C3 Flaveria. LPI values differ, as C4 Flaveria initiate leaves at a faster rate. The earlier establishment of the minor vein network and freely ending veinlets (FEV) throughout the C4 leaf and earlier offset of vein formation indicate an accelerated rate of higher order vein formation in C3 Flaveria compared with C3 Flaveria. Between the two species, ultimate leaf shape and size are equivalent but minor vein density is not (see Fig. 1, Table 1). White = central and lateral 1° veins, red = 2° veins, blue = 3° veins, yellow = 4° and higher order minor veins. Abbreviations: FEV = freely ending veinlets; LPI = leaf plastochron index.