Fig. 2

Graphical representation of the predictions of the hypothesis that delayed differentiation of petal epidermal cells, when compared to flower reproductive maturity, results in a pedomorphic corolla. Cell wall lobeyness and cell area in flower buds of a fixed size (A, C) and in mature flowers (B, D) of a non-paedomorphic species (A, B) and a pedomorphic species (C, D) are represented. Enrichment of gene sets related to cell wall lobeyness is expected in the pedomorphic species (A–D). Predicted relationships between cell wall lobeyness (CL) and position along the petal midrib (PAMR) and between cell area, log(CA), and PAMR are represented for the buds and mature flowers of the non-pedomorphic and the pedomorphic species (E). The petal midrib is drawn in cyan. The most basal position along the petal midrib is indicated with 0; the most apical position is indicated with 1. Notice that lobed cell walls decelerate cell and tissue growth (except for the petal base, which has regular and expanding cells). Petal shape differentiation into a structure with a disproportionally expanded petal base drives corolla opening and exposure of fertile flower structures. Cell wall lobeyness appears early in the non-pedomorphic species. Hence, the mature flowers of the non-pedomorphic species are small but open. Instead, cell wall lobeyness appears later in the pedomorphic species. Hence, the petal continues growing at bud-like rates until a more advanced stage. As cell walls remain regular along the whole middle rib until later, mature flowers in the pedomorphic species are large but their shape resembles that of a flower bud (expansion of the petal base and flower opening are not completed at maturity)