A functional role for the colleters of coffee flowers

Abstract

Colleters have functional definitions such as protection against dehydration, and pathogens and insects attack. So far this definition is intuitive and no direct proof has been provided. We compared flowers of coffee mutants (Decafitto), which exhibit minimal production and secretion of exudate by colleters, with normal plants, to provide a proof of concept that the exudate covering the flowers plays a role against dehydration and acts as an adhesive to keep the petals united until flower opening.

Foliar colleters inMacrocarpaea obtusifolia(Gentianaceae): anatomy, ontogeny, and secretion

“…Furthermore, the presence of pectin helps to maintain the viscous appearance of the secretion because it is a hygroscopic polysaccharide with high water absorption capacity (Nobel et al 1992). Thus, the characteristics of the secretion observed in the colleters of M. obtusifolia, together with the position of the colleters and their early differentiation, confirm the function previously described, which is assigned to colleters in general, as demonstrated in colleters of coffee flowers by Mayer et al (2013).…”

“…The mucilaginous secretion produced by the colleters is deposited on the meristems and developing tissues and organs, which ensures lubrication and protection against dehydration (Fahn 1979;Thomas et al 1989;Thomas andDave 1989a, 1989b;Thomas 1991;Evert 2006;Paiva 2009), as demonstrated in colleters of coffee flowers by Mayer et al (2013). An additional role attributed to mucilage is to act as a substrate for bacterial growth, thus facilitating symbiotic interactions (Horner and Lersten 1968;Lersten 1974aLersten , 1974bLersten 1975;Lersten and Horner 1976).…”

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

“…Lipids have been detected in the colleter secretion of species belong Apocynaceae (Appezzato-da-Glória & Estelita 2000), Leguminosae (Paiva 2009), Gentianaceae (Dalvi et al 2013), Orchidaceae (Mayer et al 2011) and Rubiaceae (Machado et al 2012;Tullii et al 2013). As claimed for polysaccharides, lipid compounds may help avoid water loss, in addition to prohibiting fungal and microorganism attack, since this hydrophobic substance lubricates the surface of young leaves and floral buds, (Fahn 1979;Thomas & Dave 1989;Thomas 1991;Evert 2006;Paiva 2009;Mayer et al 2013). Proteins have also been reported as a component of the secretion produced by colleters from a variety of different species (Thomas & Dave 1990;Klein et al 2004;Miguel et al 2006;González & Tarragó 2009;Mayer et al 2011;Dalvi et al 2013).…”

“…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).…”

Colleters in 10 species belonging to three tribes of Rubiaceae: morphoanatomical diversity and potential as useful characters for taxonomy

“…In Rubiaceae, colleters have been reported on the stipule margin and adaxial surface of leaves (Lersten 1974a;Thomas 1991), calyx adaxial surface (Robbrecht 1987;Dave et al 1988), and bracts, bracteoles, and corolla (Thomas 1991;Mayer et al 2013). Based on their external morphology and anatomical structure, the following types of colleters have been described in this family: standard, reduced standard, dendroid, brush-like, winged, and filiform (Lersten 1974a(Lersten , 1974bPuff et al 1984;Thomas 1991;Klein et al 2004;Miguel et al 2006Miguel et al , 2009Miguel et al , 2010Barreiro and Machado 2007;Vitarelli and Santos 2009;Coelho et al 2013;Mayer et al 2013;Muravnik et al 2014).…”