Fig. 6 in Quantitative analysis of diverse sporomorph-derived sporopollenins

Fig. 6. Summary and tentative conceptual sketch of evolution of sporopollenin composition within the framework plant evolution. Event 0 is the emergence of sporopollenin which is unresolved by this study. Event 1 is the loss of dominance of the saturated propyl chain. Event 2 shows a reduction to trace amounts of components with a saturated propyl chain and an increase (>5%) of the compounds without a propyl moiety (represented by VII). Event 3 represents an increase to a strong dominance (>80%) of compounds IV and V and the loss again of VII. Event 4 represents the loss of caffeic acid (V). It is assumed that caffeic acid (V) remains present in the pollen of Magnoliophyta.