Comparative and phylogenetic significance of the colleters in the family Apocynaceae

Abstract

A comparative and phylogenetic significance of colleters of 19 members of the family Apocynaceae are studied on the basis of both morphological and anatomical features. Colleters are present on the adaxial side of petiole, bract, bracteole, calyx and corolla. In many members colleters are intermingled with petiolar hairs. Structurally a colleter consists of a central core of parenchyma cells surrounded by radially elongated epithelial cells. Besides the normal structure, unicellular epithelial hair, sub‐epidermal cells, vasculature and laticifer are also observed in the colleter tissue of various genera. It is considered that the colleters are multicellular secretory structures protecting the meristem.

Stipules in Apocynaceae: an ontogenetic perspective

“…Furthermore, the stipular origin has been opposed by Thomas (1991) and Thomas and Dave (1991) because colleters occur in the five subfamilies of Apocynaceae with a predominant incidence of leaf colleters in petiolar or laminar position and/or in reproductive organs, such as the calyx and corolla ( Thomas 1991 ), where stipules could not occur. However, calycine colleters in Apocynaceae do not arise from the base of the sepals, but from the adaxial face of a higher portion of the connate calyx ( Demarco 2008 ), resembling the origin of laminar colleters in leaves.…”

“…Colleters are secretory structures present in vegetative and/or reproductive organs that produce a sticky fluid, composed only of mucilage and/or lipophilic compounds, which protects meristems ( Fahn 1979 , 1990 ; Thomas 1991 ). In Apocynaceae, the colleter generally is a non-vascularized emergence occurring on the leaf, cotyledons, bracts, bracteoles, sepals, and corolla ( Thomas 1991 ; Sennblad et al 1998 ; Canaveze and Machado 2015 ) whose secretion may protect buds and developing organs against desiccation, herbivores and/or fungal proliferation ( Demarco 2008 ).…”

Comparative systematic study of colleters and stipules of Rhizophoraceae with implications for adaptation to challenging environments

“…A few genera of Apocynaceae (Nerium L. and Alstonia R.Br.) also have large colleters, up to 1100 μm in length (Thomas & Dave, 1991), but are less abundant (10-35 colleters) than in the mangrove Rhizophoraceae, and do not occur in stipules, but on petioles. However, a complication in providing a clear summary is that some species have broad elevational ranges.…”

“…Although many studies of colleters have been carried out in Rubiaceae (Lersten, 1974a, b, ; Miller, Scott & Gardner, ; Mangalan et al ., ; Klein et al ., ), Apocynaceae (Thomas & Dave, , ; Appezzato‐da‐Glória & Estelita, ; Schwarz & Furlan, ) and Myrtaceae (da Silva et al ., ), colleters of Rhizophoraceae have been less comprehensively studied beyond mangrove taxa (Lersten & Curtis, ; Sheue et al ., ). However, Rhizophoraceae is a family well suited to the examination of the idea that colleters have an important role in protecting the developing shoot, because members of this family are distributed over a broad range of environments, including mangrove habitats, lowland forests and montane forests.…”

Anatomia ecológica do limbo foliar e de coléteres de espécies da tribo Coussareeae Benth & Hook. F. (Rubiaceae)

“…É o tipo mais comum encontrado na família, sendo relatado em diversos estudos, em diferentes órgãos, como estípulas (Klein et al 2004;Miguel et al 2009;Muravnik et al 2014), flores (Mayer et al 2013) e bractéolas (Judkevich et al 2017). O tipo padrão também foi observado em outras famílias da ordem Gentianales, como Apocynaceae (Thomas, Dave, 1991;Ribeiro et al 2017).…”