Morphology and evolution of laticifers in Moraceae

Abstract

Laticifers are specialized cells in the secretion of latex, a suspension of various dispersed particles in a liquid with different refractive index. Morphologically, the laticifers are divided into four types: non-articulated unbranched, non-articulated branched, articulated anastomosing and articulated anastomosing. In Moraceae, the laticifers are considered a synapomorphy, and despite some anatomical studies suggest a variety of types of this structure in the family, they are generally classified as non-articulated and branched. The lack of ontogenetic studies of laticifers in the family probably led to their misclassification in the species. Moreover, as the latest phylogeny of Moraceae established more clearly the relationship between the tribes, the family constitutes a good model to contribute to the knowledge of both the anatomy and evolution of laticifers, since the studies of the evolution of secretory structures are rare. Thus, this work has as main objectives: (1) to study the anatomy and development of laticifers in species belonging to six tribes of the family Moraceae, (2) to identify the action of pectinases and cellulases in the laticifer wall formation in two species; and (3) trace the evolution of this secretory structure in the group. To this end, reproductive apical meristems of nine species of the family Moraceae covering the six tribes will be collected, fixed in Karnovsky and processed for analysis under light microscopy. Two species will be chosen for cytochemical analysis in transmission electron microscopy. A matrix of characters of laticifers will be elaborated.