Anatomical characterisation of the foliar colleters in Myrtoideae (Myrtaceae)

Abstract

Colleters are secretory structures that occur in vegetative or reproductive shoot apices of many botanical families. However, in the order Myrtales, reports of colleters have considered only external morphology. We therefore evaluated apical meristems of 52 species belonging to 17 genera from seven tribes of subfamily Myrtoideae (Myrtaceae), so as to analyse the incidence and morphological types of colleters. The samples were fixed for light and scanning electron microscopy. Histochemical tests were carried out on fresh and methacrylate-embedded material. Proteins of the colleter secretions were analysed by SDS-PAGE. We have classified and described the following three new colleter types: petaloid, conic and euryform. None of the species contained all three colleter types. The petaloid colleters were present in three tribes (Syzygieae, Melaleuceae and Lophostemoneae). The conic colleters were observed in three tribes (Leptospermeae, Myrteae and Melaleuceae) and the euryform type occurred in five tribes (Leptospermeae, Syncarpieae, Myrteae, Syzygieae and Melaleuceae). In the tribe Eucalypteae, we found no evidence of colleters. The presence of mucilaginous secretion that defines colleters was confirmed by histochemical tests, and no proteins were found in the secretion. The colleters in Myrtoideae may help clarify the phylogenetic relationships of the Myrtaceae family.

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

“…Chamaecrista and Caliciopsis studied, non-vascularized colleters have bee previously reported for other species of Chamaecrista belonging to other sections (De-Paula & Oliveira 2007;Coutinho et al 2013;, other species of Caesalpinioideae (Paiva & Machado 2006b;Paiva 2009;Souza 2014), and even species of other families (Paiva & Machado 2006a;Paiva 2009;Vitarelli & Santos 2009;Silva et al 2012;Dalvi et al 2013). Anatomically, the colleters described for the species of sect.…”

“…The diversity of types and different positions reported for colleters in Chamaecrista, both by us and other authors, emphasizes how important and poorly understood this structure is. Such data promise to be useful for both taxonomic and phylogenetic studies, as has been the case for other taxa (Lersten 1975;Curtis & Lersten 1980;Thomas 1991;González 1998;Simões et al 2006;González & Tarragó 2009;Sheue et al 2012;Silva et al 2012;Vitarelli et al 2015;Fernandes et al 2016). However, further studies are necessary to thoroughly evaluate the evolutionary history of colleters in Chamaecrista.…”

“…Although Lersten (1974) pointed out that the standard type of colleter is the most widespread, variation in the morphoanatomy of these structures has since been observed such that now several different types of colleters are recognized (Mayer et al 2011;Silva et al 2012;Coutinho et al 2015). Standard type colleters are comprised of a secretory palisade epidermis covering a non-secretory central axis, which may or may not be vascularized with xylem and phloem (Lersten 1974).…”

“…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).…”

“…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;.…”