Laticifers in vascular plants

• Autor(a) principal: Maximo, Erika de Carvalho Prado Noronha
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: http://www.teses.usp.br/teses/disponiveis/41/41132/tde-12122019-105221/
• topic: Distribuição; Distribution; Ductos resiníferos; Idioblastos fenólicos; Latex; Látex; Laticíferos; Laticifers; Phenolic idioblasts; Plantas vasculares; Resin ducts; Vascular plants

Laticifers are specialized cells that secrete latex, a complex mixture of metabolites whose main function is defense against herbivory. Laticifers are present in several families of vascular plants and their occurrence is considered as a taxonomic and often phylogenetic indicator. There are many misinterpretations in the literature attributing the presence of laticifers in families that do not have them. Thus, a comprehensive review of this structure and its actual distribution and evolution is necessary. The objectives of the present work are to describe laticifers structurally, distinguishing them from other secretory structures and correcting any description errors; to comparatively evaluate the composition of latex in the different families of latescent plants; to identify the type of laticifer in each family based on their ontogenesis; and to evaluate their actual distribution and evolution in vascular plants. Although the secretions of laticifers and resin ducts are similar in color and the diversity of metabolites, latex is an intracellular secretion that consists of the very protoplast of laticifers, while the resin of ducts is an extracellular secretion that has no structural components in its composition. In addition, latex is a secretion specific to laticifers and laticifers are conceptually rows of cells, while ducts are formed by an epithelium that delimits a lumen; therefore, they do not fall under this classification. As for the metabolites present in latex, we have identified lipids, proteins, phenolic compounds, carbohydrates, and alkaloids in the various families of latescent plants, evidencing the important evolutionary convergence that occurred in the various lines of vascular plants. With relation to the distribution of laticifers, we have found that of the 63 families analyzed, only 34 have latex in at least one of their representatives. Many of these families have no phylogenetic relationship, demonstrating that laticifers emerged multiple times in the evolution of vascular plants. We have demonstrated that 18 so-called latescent families actually have resin ducts or secretory idioblasts instead of laticifers. We have also ascertained that all laticifers are articulated and can be classified as anastomosed or non-anastomosed, branched or unbranched, thereby refuting the existence of laticifers classified as non-articulated. Finally, we also refute the intrusive autonomous growth theory since there is no evidence of its occurrence in any of the latescent families. This study makes a very significant contribution to the understanding of laticifers regarding their identification, latex composition, distribution, growth and evolution in vascular plants