Structural, Functional and Phylogenetic Aspects of the Colleter

Abstract

This article surveys the structural, functional and phylogenetic significance of colleters in different dicotyledonous families. Colleters are multicellular secretory structures attached to the stipule, petiole, lamina, bract, bracteole, calyx and corolla. Colleters are grouped into standard (S), dendroid (D) and brush-like (B) types on the basis of their morphology and structure. D and B-type colleters occur in certain members of Rubiaceae that also have bacterial leaf nodules. Besides the normal structure, epithelial hairs, thin-walled subepidermal cells, laticifers and vasculature are present in many colleters of Apocynaceae. It is probable that the colleter functions to protect the developing meristem by secreting a viscous fluid. Exudate of D-type colleters are mucilaginous, providing the substrate necessary for the nutrition of endophytic bacteria.

Colleters in Chamaecrista (L.) Moench sect. Chamaecrista and sect. Caliciopsis (Leguminosae-Caesalpinioideae): anatomy and taxonomic implications

“…Chamaecrista and Caliciopsis are indeed colleters. Such structures are typically related to the protection of young leaves and flowers from desiccation and attack from microorganisms since the secretion present is made of mucilage or a mixture of mucilage, resin and protein (Thomas & Dave 1989;Thomas 1991;Rocha et al 2009). …”

“…Colleters are secretory structures that are usually found on the adaxial side of vegetative and/or reproductive structures such as stipules, bracts, sepals and petals (Fahn 1979;Thomas 1991;Mayer et al 2013;Coutinho et al 2015). The viscous exudates secreted by colleters are said to be involved in lubrication, desiccation prevention and protection from microbial attacks of young and developing organs (Fahn 1979;Thomas 1991;Mayer et al 2013;Coutinho et al 2015).…”

“…There are several types of colleters, which may originate from protodermal cells only or from all primary meristems (Lersten 1974;Thomas 1991;Appezzato-da-Glória & Estelita 2000;Rio et al 2002;Silva et al 2012;Coutinho et al 2015). Therefore, to properly evaluate the presence of colleters in plants, their morphoanatomy, position and both time and composition of the secretion must be considered in order to avoid erroneous interpretations since such structures share morphoanatomical similarities with other secretory structures (Solereder 1908;Inamdar et al 1986;Subramanian et al 1989;Thomas 1991;Coutinho et al 2015).…”

“…Therefore, to properly evaluate the presence of colleters in plants, their morphoanatomy, position and both time and composition of the secretion must be considered in order to avoid erroneous interpretations since such structures share morphoanatomical similarities with other secretory structures (Solereder 1908;Inamdar et al 1986;Subramanian et al 1989;Thomas 1991;Coutinho et al 2015).…”

“…The presence and types of colleters are useful characters for taxonomic studies and have been reported for more than 60 families (Thomas 1991;Rio et al 2005;Simões et al 2006;Silva et al 2012;Dalvi et al 2013;Coutinho et al 2015). In Chamaecrista, colleters have been described in vegetative and reproductive organs of species belonging to sections Absus, Apoucouita, Grimaldia, Chamaecrista and Xerocalyx (Coutinho et al 2013;.…”