Trends of fruit morphogenesis in Pandanaceae: comparative carpology of Freycinetia Gaudich

Abstract

With the current reassessment of the phylogeny of Pandanales, revealing the peculiarities of fruit structure of representatives of the order, as well as determination of apomorphies and plesiomorphies of the families included in the order are of importance. With the aim to fill in gaps in the data on fruit structure and to determine principal trends of fruit morphogenesis in Pandanaceae, the present study focused on pericarp anatomy in the genus Freycinetia, fruits of which are traditionally referred to as berries. The present investigation confirmed the lack of a continuous sclerenchymatous zone in the pericarp of Freycinetia species, and the fruit is treated as a superior paracarpous berry of Nuphar type. Fusiform groups of longitudinally elongated sclereids are revealed in the mesocarp of Freycinetia palawanensis (incertae sedis) and F. graminifolia (section Solmsiella). Since this character is treated as specific for the subgenus Gaudichaudiella, the inclusion of these two studied species in this subgenus is proposed. The principal carpological plesiomorphies and apomorphies of the family are outlined, and two scenarios for fruit morphogenesis, from berries to ‘drupaceous’ fruits and vice versa, are proposed.