New perspectives on secretory structures in Clusia (Clusiaceae - Clusiod clade): production of latex or resins?

Abstract

The Clusioid clade is quite diverse, encompassing the five families Clusiaceae, Bonnetiaceae, Calophyllaceae, Hypericaceae, and Podostemaceae. However, its members have important synapomorphies, such as the presence of xanthones, polyisoprenylated benzophenones, and quinones, as well as schizogenous secretory ducts and cavities, and tenuinucellate ovules. Owing to the milky appearance of the exudate present in ducts of these families (except Bonnetiaceae), many authors have referred to this secretion as latex, while others have preferred to use the term resin. Faced with this confusion about the description of the exudate present in Clusiaceae, the aim of this study was to identify which classes of substances are being produced by those structures in the genus Clusia, compared with other members of Clusiaceae and the Clusioid clade in general. Furthermore, we describe the structure and distribution of the secretory ducts in species of Clusia, as well as a detailed histochemical study. These secretory ducts secrete an exudate of variable composition, but predominantly terpenic. We conclude that Clusia, as well as some representatives of the Clusioid clade, do not have latex but resiniferous secretory ducts.