title: Foliar secretory structures in Crotoneae (Euphorbiaceae): Diversity, anatomy, and evolutionary significance.
abstract: OBJECTIVE
  Phylogenetic and morphological studies have helped clarify the systematics of large and complex groups such as the tribe Crotoneae (Euphorbiaceae). However, very little is known about the diversity, structure, and function of anatomical features in this tribe. Crotoneae comprises the species-rich pantropical genus Croton and six small neotropical genera. Here we characterized the anatomy of leaf secretory structures in members of this tribe and explored their function and evolutionary significance.
  
  
  METHODS
  Young and mature leaves of 26 species were studied using standard anatomical light microscopy techniques. Three sections of Croton and one representative of Brasiliocroton and Astraea were sampled.
  
  
  RESULTS
  We identified five types of secretory structures: laticifers, colleters, extrafloral nectaries, idioblasts, and secretory trichomes. Laticifers were present in all species studied except Croton alabamensis, which instead presented secretory parenchyma cells. Articulated laticifers are reported in Crotoneae for the first time. Colleters of the standard type were observed in the majority of the sampled taxa. Extrafloral nectaries were present in section Cleodora and in B. mamoninha, but absent in section Lamprocroton and Astraea lobata. Idioblasts were spread throughout the palisade and/or spongy parenchyma in most of the studied species. Secretory trichomes were restricted to Lamprocroton except for C. imbricatus.
  
  
  CONCLUSIONS
  This study revealed a high diversity of secretory structures, including novel ones, in one of the largest clades of Euphorbiaceae. Our results are promising for investigations on the anatomical and ecophysiological bases of species diversification within Euphorbiaceae.
authors.affiliation: Universidade Federal de Viçosa, DBV, Viçosa 36570-900, Brazil.
authors.forename: Narah C
authors.initials: NC
authors.lastname: Vitarelli
authors.affiliation: Real Jardín Botánico, RJB-CSIC, Plaza de Murillo 2, ES-28014, Madrid, Spain.
authors.forename: Ricarda
authors.initials: R
authors.lastname: Riina
authors.affiliation: Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo, Diadema, SP, Brazil Instituto de Botânica, Secretaria do Meio Ambiente, Cx. Postal 3005 01061-970, São Paulo, SP, Brazil.
authors.forename: Maria Beatriz R
authors.initials: MB
authors.lastname: Caruzo
authors.affiliation: Instituto de Botânica, Secretaria do Meio Ambiente, Cx. Postal 3005 01061-970, São Paulo, SP, Brazil.
authors.forename: Inês
authors.initials: I
authors.lastname: Cordeiro
authors.affiliation: Real Jardín Botánico, RJB-CSIC, Plaza de Murillo 2, ES-28014, Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Fuertes-Aguilar
authors.affiliation: Universidade Federal de Viçosa, DBV, Viçosa 36570-900, Brazil.
authors.forename: Renata M S A
authors.initials: RM
authors.lastname: Meira
mesh_terms: D044822:Biodiversity; D005075:Biological Evolution; D019665:Euphorbiaceae / Q000033:anatomy & histology* / Q000166:cytology; D010802:Phylogeny; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000166:cytology; D013045:Species Specificity
keywords: Astraea; Brasiliocroton; Croton; Euphorbiaceae; anatomy; colleters; extrafloral nectaries; laticifers; secretory idioblasts; secretory trichomes