title: Extrafloral nectaries in neotropical Gentianaceae: occurrence, distribution patterns, and anatomical characterization.
abstract: OBJECTIVE
  Extrafloral nectaries (EFNs) are structures that secrete nectar and protect plants against herbivores and pathogens. In Gentianaceae, these structures have been described in species of Calolisianthus, Fagraea, and Anthocleista and are important morphological markers for taxonomic and phylogenetic studies. To establish a foundation for further studies, we investigated the occurrence, distribution patterns, and anatomy of EFNs on leaves of 27 species belonging to 13 genera and three tribes of neotropical Gentianaceae. •
  
  
  METHODS
  Leaf samples were diaphanized, stained with basic fuchsin, and mounted in glycerinated gelatin. Cross sections were obtained from material embedded in methacrylate or paraffin, stained, and mounted in Permount. Polysaccharides were histochemically stained with periodic acid-Schiff stain. Samples were also examined with scanning electron microscopy. •
  
  
  RESULTS
  Unusual EFNs, visible only with light microscopy, were formed of modified epidermal cells. Each EFN consisted of 2-5 secretory cells encircling a central cell. The EFNs varied in size and in the shape and arrangement of the adjacent cells surrounding the secretory cells. EFNs occurred in all analyzed species as isolated units distributed throughout the leaf blade or as aggregates; aggregates were generally visible to the naked eye. Based on their occurrence as aggregates or isolated units and on their location on the leaf blade, six distribution patterns were identified. •
  
  
  CONCLUSIONS
  This is the first comprehensive study of EFNs on the leaves of neotropical Gentianaceae. The data suggested that NEFs evolved from isolated units for NEFs in aggregates. The results represent a new source of data for future ecological, systematic, and phylogenetic studies in Gentianaceae.
authors.affiliation: Departamento de Biologia Vegetal, Universidade Federal de Viçosa (UFV), Av. P.H. Rolfs, s/n, Campus Universitário, CEP 36570-000, Viçosa, Minas Gerais, Brasil.
authors.forename: Valdnéa Casagrande
authors.initials: VC
authors.lastname: Dalvi
authors.forename: Renata Maria Strozi Alves
authors.initials: RM
authors.lastname: Meira
authors.forename: Aristéa Alves
authors.initials: AA
authors.lastname: Azevedo
mesh_terms: D005075:Biological Evolution; D001938:Brazil; D029965:Gentianaceae / Q000033:anatomy & histology*; D019441:Plant Epidermis / Q000033:anatomy & histology; D018515:Plant Leaves / Q000033:anatomy & histology*; D057048:Plant Nectar; D054046:Plant Stomata / Q000033:anatomy & histology; D013045:Species Specificity
chemical_list: D057048:Plant Nectar
keywords: Chironieae; Coutoubeinae; Helieae; Saccifolieae; epidermal nectaries; foliar anatomy; nectarioles; secretory structures