The mechanism of plication inception in palm leaves; problem and developmental morphology.

As the first part of a general reinvestigation of the mechanism of plication inception in palms, the present paper reviews the past literature and describes the overall morphogenesis of leaves of Chrysalidocarpus lutescens, Chamaedorea seifrizii, and Rhapis excelsa as observed principally with the scanning electron microscope. Plication inception in the pinnate leaf of Chrysalidocarpus begins when the leaf is 700–800 μm in length and continues until it is approximately 5–6 mm in length or after 40–42 pleats have been initiated. Initiation is bidirectional with the majority of folds being added basipetally. Plications initiated in the apical region of the leaf are vertically oriented but become reoriented to a more horizontal plane as a result of greater elongation in the abaxial part of the rachis. The adaxial portion of the plications is covered to varying degrees by a marked adaxial outgrowth of the rachis axis. But as the lamina continues to grow in surface, the plications grow beyond this rachis plug ...