title: Ontogenesis and functions of saxophone stem in Acrocomia aculeata (Arecaceae).
abstract: OBJECTIVE
  The underground saxophone stem systems produced by seedlings of certain palm species show peculiar growth patterns and distinctive morphologies, although little information is available concerning their development and function. We studied the ontogenesis of the saxophone stem in Acrocomia aculeata, an important neotropical oleaginous palm, and sought to experimentally define its function.
  
  
  METHODS
  Morpho-anatomical evaluations were performed during 240 d on seedlings using traditional methodologies. The tuberous region of the structure was submitted to histochemical tests and evaluated by transmission electron microscopy. The aerial portions of 130 1- to 3-year-old greenhouse plants were removed and their continuous growth capacity was evaluated after 30 d. Severed saxophone stems were also stored at room temperature (average 25 °C) for up to 90 d and then cultured for 60 d to evaluate root and shoot emission.
  
  
  RESULTS
  The development of the saxophone stem is distinct from other underground systems previously described, and involves three processes: growth and curvature of the cotyledonary petiole, expansion and curvature of the hypocotyl, and expansion of the plumule internodes. The tuberous region stores water and starch, as well as lesser amounts of mucilage and oil. Growth of the aerial portion occurred in 84 % of the separated saxophone stems and in 53 % of the stems held in storage.
  
  
  CONCLUSIONS
  The saxophone stem represents an important adaptation of A. aculeata to anthropogenically impacted and/or dry environments by promoting the burial of both the shoot meristem and storage reserves, which allows the continuous growth of aerial organs.
authors.affiliation: Departamento de Biologia Geral, Universidade Estadual de Montes Claros, 39401-089 Montes Claros-MG, Brazil.
authors.forename: Joyce Nascimento
authors.initials: JN
authors.lastname: E Souza
authors.affiliation: Departamento de Biologia Geral, Universidade Estadual de Montes Claros, 39401-089 Montes Claros-MG, Brazil leonardo.ribeiro@unimontes.br.
authors.forename: Leonardo Monteiro
authors.initials: LM
authors.lastname: Ribeiro
authors.affiliation: Departamento de Biologia Geral, Universidade Estadual de Montes Claros, 39401-089 Montes Claros-MG, Brazil.
authors.forename: Maria Olívia
authors.initials: MO
authors.lastname: Mercadante-Simões
mesh_terms: D028023:Arecaceae / Q000033:anatomy & histology / Q000254:growth & development* / Q000502:physiology; D018546:Hypocotyl / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology; D018547:Plant Stems / Q000033:anatomy & histology / Q000254:growth & development* / Q000502:physiology; D035281:Plant Tubers / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology; D036226:Seedlings / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology
keywords: Acrocomia aculeata; hypocotyl; ligule; ontogenesis; palms; seedling; underground system