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

Abstract

Colleters are common secretory structures in Rubiaceae. In this study, we describe colleter morphoanatomy and histochemistry in 10 species belonging to Chiococceae, Coussareae, and Psychotrieae tribes of Rubiaceae. Colleter morphoanatomy was analyzed by light and scanning electron microscopy. Microscopy analysis revealed that colleters were present on the stipule adaxial surface in all species. In the case of Palicourea marcgravii A.St.-Hil. and Chiococca alba Hitchc., colleters were also found on leaf primordia and at the stipule apex, respectively. Colleters were classified into three types: standard, bifurcated standard, and reduced standard. Further analysis showed that colleter epidermal cells are thin-walled and possess a thin cuticle, conspicuous nuclei located at the equatorial or basal region, and abundant cytoplasm. Intercellular spaces were found among epidermal cells in Chiococca alba, Coussarea triflora Müll.Arg., Coussarea verticillata Müll.Arg., Psychotria conjungens Müll.Arg., and Psychotria sessilis Vell. Crystalliferous idioblasts containing raphides were observed in the colleter central parenchymatous axis of all species, while crystal sand was found only in Chiococca alba. Histochemical tests revealed that colleter secretion is composed of a mixture of mucilage and protein. We conclude that colleter position, typological variation, presence of vascularization, and type of calcium oxalate crystals represent promising characters for future taxonomic and phylogenetic studies in Rubiaceae. Résumé: Les collétères sont des structures sécrétoires communes chez les Rubiaceae. Dans cette étude, les auteurs décrivent la morpho-anatomie et l'histochimie de collétères de 10 espèces appartenant aux tribus des Chiococceae, Coussareae et Psychotrieae des Rubiaceae. La morpho-anatomie de collétères a été analysée par microscopie optique et microscopie électronique à balayage. L'analyse en microscopie a révélé que les collétères étaient présentes sur la surface adaxiale des stipules de toutes les espèces. Dans le cas de Palicourea marcgravii A.St.-Hil. et Chiococca alba Hitchc., les collétères se trouvaient aussi sur les ébauches foliaires et à l'apex des stipules, respectivement. Les collétères ont été classifiées en trois types : standard, standard bifurqué et standard réduit. Des analyses supplémentaires ont montré que les cellules épidermiques des collétères possèdent une paroi et une cuticule minces, un noyau bien évident localisé dans la région équatoriale ou basale, et un cytoplasme abondant. Des espaces intercellulaires ont été trouvés entre les cellules épidermiques chez Chiococca alba, Coussarea triflora Müll.Arg., Coussarea verticillata Müll.Arg., Psychotria conjungens Müll.Arg. et Psychotria sessilis Vell.Des idioblastes cristallifères contenant des raphides ont été observés dans l'axe parenchymateux central des collétères de toutes les espèces, alors qu'un sable cristallin était trouvé seulement chez Chiococca alba. Des tests histochimiques ont révélé que la sécrétion des collétères est composée d...

Leaf and sepal colleters in Calolisianthus speciosus Gilg (Gentianaceae): a morphoanatomical comparative analysis and mechanisms of exudation

“…Morphologically distinct types of colleters have been reported in the literature (Lersten 2008;Thomas 1991;Silva et al 2017), and the distribution, typology and the presence of calcium oxalate crystals are characters frequently used in taxonomic (Lersten 1974;Coutinho et al 2015;Lopes-Mattos et al 2015) and evolutionary approaches (Vitarelli et al 2015;Judkevich et al 2017). The standard colleter type, formed by a non-secretory parenchyma axis covered by palisade secretory epidermis (Fahn 1988;Thomas 1991), is the most common and has been recorded in several unrelated families such as Euphorbiaceae (Machado et al 2015;Vitarelli et al 2015;Feio et al 2016), Rubiaceae (Lopes-Mattos et al 2015Judkevich et al 2017) and Salicaceae (Fernandes et al 2016;Faria et al 2019), but only for Macrocarpea obtusifolia in Gentianaceae (Dalvi et al 2014a).…”

New registers of colleters in species of Myrtaceae from Brazilian Cerrado

“…Colleters are widely distributed on young vegetative and reproductive organs in plants and have been reported in ferns (Oliveira et al 2017), monocots (Leitão & Cortelazzo 2008;Mayer et al 2011;Cardoso-Gustavson et al 2014) and in sixty-five eudicots families (Thomas 1991;Muravnik et al 2014) such as Apocynaceae, Gentianaceae, Rubiaceae, (Thomas 1991;Renobales et al 2001;APG 2009;Lopes-Mattos et al 2015;Tresmondi et al 2015). Anacardiaceae (Lacchia et al 2016), Aquifoliaceae (González & Tarragó 2009), Euphorbiaceae (Machado et al 2015;Vitarelli et al 2015), Fabaceae (Barros & Teixeira 2016), Lecythidaceae (Paiva 2012), Moraceae (Machado et al 2013), Rutaceae (Macêdo et al 2016), Rhizophoraceae (Sheue et al 2012) and Myrtaceae (Silva et al 2012).…”

Colleters inCasearia(Salicaceae): a new interpretation for the theoid teeth

“…Colleters produce a sticky secretion that functions as a lubricant, protecting meristems and developing organs against desiccation and attack by pathogens (Thomas, ; Mayer, Cardoso‐Gustavson & Appezzato‐Da‐Glória, ; Mayer, Carmello‐Guerreiro & Mazzafera, ). Colleters occur on the adaxial surface of young reproductive and (or) vegetative organs in several families of eudicots (Fahn, ; Thomas, ; Klein et al ., ; Martins, ; Coelho et al ., ; Dalvi et al ., ; Lopes‐Mattos et al ., ) and only Orchidaceae among monocots (Leitão & Cortelazzo, ; Mayer et al ., ). Recently, colleters have also been reported at the leaf margins for some species (Paiva, ; Mercadante‐Simões & Paiva, ; Vitarelli et al ., ; Feio, Riina & Meira, ).…”