Abscission-Like Leaflet Separation in Chamaedorea seifrizii (Arecaceae)

In monocots, the ability to form compound leaves is restricted to a few families. In the palm family Arecaceae, compound leaves develop through leaflet separation by an abscission-like process. The purpose of this study was to compare this process in Chamaedorea seifrizii with that previously described in Chamaedorea elegans, putting the emphasis on the separation of an initially simple lamina into individual leaflets. Although the overall sequence of events forming pinnate leaves in these two palms is similar, the timing of events differs strikingly and has implications for late developmental processes. In both species, leaflet separation occurs through formation of separation sites, schizogeny at these sites, mechanical rupture, and deposition of protective substances. Early separation in C. seifrizii results in differentiation of ground meristem cells, exposed to the leaf surface by schizogeny, as epidermal cells. Although a few of the separation site cells do not reach full mature epidermal cell size, all deposit a continuous cuticle on the surface of the leaflet margin. In contrast, ground cells at the separation site are exposed much later in C. elegans and deposit suberin-like substances in their cell walls rather than forming a continuous cuticle. [PUBLICATION ABSTRACT]