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

Abstract

Salicaceae possess a range of leaf teeth types, many characterized as nectariferous salicoid or violoid teeth. One large genus, Casearia, deviates from this generalization in having theoid teeth. Although taxonomic descriptions of Casearia have included reports of glands at the apex of teeth, there have been no descriptions of their anatomy or functional role. Here, we aim to describe the anatomy of the theoid teeth of 43 Casearia spp. Leaf samples from herbarium specimens were processed for light and scanning electron microscopy. Leaves of C. sylvestris were collected and fixed in the field for histochemical tests, revealing only polysaccharides in secretory epidermal cells and outside of these cells. The glands have precocious development and are composed of a non-vascular central axis covered with a palisade-like secretory epidermis. During senescence, the cells of the palisade-like secretory epidermis and central axis appear to lose their typical form, with some cell walls disintegrating. In the mature leaf, an abscission zone at the base of the gland causes detachment of the gland. The placement, anatomical structure, precocious activity and polysaccharide secretion (in C. sylvestris) allow the recognition of the glands associated with the marginal teeth in Casearia as colleters. Similar studies are needed for other genera in order to clarify how colleters have evolved in Salicaceae and how they are functionally and anatomically related to other teeth types in the family.

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). Colleters with large intercellular spaces that accumulate secretion, as reported here for C. speciosus, seem to be common for species of Gentianaceae both in the Neotropics (Delgado et al 2011;Dalvi et al 2020) and in the temperate region (Renobales et al 2001).…”

Muito além de um dente: ocorrência de hidatódios nos dentes foliares de Hydrocotyle asterias Cham. & Schltdl. (Araliaceae Juss.)

“…Estudos que investigaram a anatomia dos dentes foliares evidenciaram que a associação destes com estruturas secretoras, suscitando novas indagações inerentes ao papel taxonômico e ecológico dos dentes foliares (Thadeo, Azevedo & Meira 2014, Fernandes et al 2016. Nectários extraflorais com tricomas nectaríferos foram encontrados no ápice dos dentes foliares de Triumfetta semitriloba Jacq.…”

“…Em Salicaceae, estudos anatômicos revelaram que, de acordo com a espécie, o dente teoide pode ocorrer associado à coléteres ou hidatódios, apresentando características de importante aplicação taxonômica (Thadeo, Azevedo & Meira 2014, Fernandes et al 2016. Esses dados ratificam a importância de se conhecer a composição dos dentes foliares, uma vez que podem amplificar o entendimento estrutural e funcional dessa região da folha para as plantas (Melo- de-Pinna 2004, Nicolas & Plunkett 2009.…”

“…Três tipos de glândulas foram descritas associadas aos dentes foliares: coléteres, hidatódios e nectários. Coléteres já foram confirmados nos dentes foliares de espécies das famílias Aquifoliaceae (Gonzalez & Tarragó 2009), Euphorbiaceae (Vitarelli et al 2015), Lecythidaceae (Paiva 2012), Rosaceae (Chin et al 2013) e Salicaceae (Fernandes et al 2016). Hidatódios foram reportados para Asteraceae (Castro, Leitão-Filho & Monteiro 1997, Melo-de-Pinna 2004, Milan, Hayashi & Appezzato-da-Glória 2006, Chloranthaceae (Field et al 2005) e Salicaceae (Thadeo, Azevedo & Meira, 2014).…”

A new species of Casearia (Samydoideae, Salicaceae) from South Africa

“…Molecular phylogenetic analyses support Samydoideae as monophyletic, but some researchers still prefer to treat it at family level, namely a narrowly circumscribed Samydaceae (Samarakoon 2015). Diagnostic characters for the Samydoideae include loss of petals, presence of partly deciduous theoid (sensu Fernandes et al 2016) leaf teeth, and leaf blades with pellucid punctations and/or lines (Fernandes et al 2018). Based on DNA sequence data, four major clades are well supported, each being recognized at tribal level, with Casearia belonging to tribe Samydeae (Samarakoon 2015).…”