Abstract
Abstract: Diploon is a monospecific genus represented by Diploon cuspidatum, an arboreal species that has morphological characteristics distinct from those of other Sapotaceae species. In this study, Diploon cuspidatum leaves were characterized morphoanatomically in order to reveal additional diagnostic characters of their external morphology of the genus. The Diploon petiole presents shape and arrangement of the vascular system flat-convex, occasionally with one or two accessory bundles, many laticifers, and many prismatic crystals. The midrib is biconvex with a U-shaped cuticle on the abaxial side, and laticifers are associated with the vascular tissues. Mesophyll is dorsiventral, palisade parenchyma has two cell layers, T- and Y-shaped malpighiaceous trichomes are on the abaxial epidermis with a small stalk cell and long arm. The venation pattern is brochidodromous. Intersecondary veins run parallel to the secondary veins, and quaternary veins branch freely. Higher order veins are not present. Morphoanatomical analysis revealed important characteristics that reveal a set of structures common to Sapotaceae, in addition to characters that are important for the recognition and identification of D. cuspidatum.
Highlights
Sapotaceae is a family with a pantropical distribution that includes about 60 genera and 1300 species (Pennington 1991; Govaerts et al 2001, The PlantList 2013)
Diploon is a monospecific genus represented by Diploon cuspidatum (Hoehne) Cronquist, which has as its basionym Chrysophyllum cuspidatum Hoehne
The analysis of leaf architecture allowed the identification of a brochidodromous venation pattern with a pinnate midrib (Figure 2a)
Summary
Sapotaceae is a family with a pantropical distribution that includes about 60 genera and 1300 species (Pennington 1991; Govaerts et al 2001, The PlantList 2013). Diploon is a monospecific genus represented by Diploon cuspidatum (Hoehne) Cronquist, which has as its basionym Chrysophyllum cuspidatum Hoehne This arboreal species has alternating leaves, axillary flowers, basally connate petals, and it lacks staminodes. Its ovary is glabrous and unilocular with two ovules, and it has basal placentation, in addition to succulent fruits containing a single seed that has a small, basilateral scar and no endosperm (Pennington 1990, 1991). Together, these characters contribute to a good generic delimitation because some features of the genus Diploon are not common in other Sapotaceae, which facilitates its identification. Despite having a distinct reproductive morphology (unilocular ovary and biovular with basal placentation), Diploon shares morphological, anatomical, chemical, and phylogenetic characteristics with other Sapotaceae genera (Cronquist 1946, Kukachka 1979, Pennington 1990, Swenson & Andeberg 2005)
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