Morphoanatomical characterization of Gentianaceaes species from cerrado and campo rupestre in Minas Gerais / Caracterização morfoanatômica de espécies de Gentianaceae ocorrentes em áreas de cerrado e de campo rupestre em Minas Gerais

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The family Gentianaceae presents between 1600 and 1700 species predominantly herbaceous. In Brazil, 25 genera of this family occur mainly in the Cerrado and campos rupestres. The species are included into 6 tribes and 86 genera. The tribe Chironieae presents around 159 species distributed into 23 genera, such as Schultesia and Deianira. The tribe Helieae exhibits 184 species in 22 genera among them Calolisianthus. The taxonomic limit between the Gentianaceaes species is confuse, usually, and needs to be elucidated. The preset work aimed at the understanding of some strategic adaptations of the species from the genera Deianira, Schultesia, and Calolisianthus through the contribution of morphoanatomic data of some Gentianaceaes species, offering, therefore, subsidies for clarifying the taxonomy of these genera. The samples were collected in the Cerrado of FLONA of the municipality of Paraopeba, Minas Gerais State, Brazil, and in the campo rupestre of Serra de Ouro Branco Minas Gerais State, Brazil, and processed according to the general techniques for studies using light and scanning electron microscopies. The species studied were the following ones: Deianira erubescens, Deianira pallescens, Deianira nervosa, Deianira chiquitana, Schultesia gracilis, Calolisianthus pendulus, Calolisianthus amplissimus, and Calolisianthus speciosus. Deianiras species present roots with cortex formed by parenchyma with starch grains, Arumtype arbuscular mycorrhyzae, usual secondary growth (D. pallescens and D. chiquitana) or non-usual with interxylary phloem (D. erubescens and D. nervosa); amphistomatic leaves (excepting D. nervosa whose leaves are hypostomatic), homogenous mesophyll, on most species, or dorsiventral one in D. nervosa, caps of fibre or sclereids associated to the bundle. S. gracilis presents roots with aerenchyma and Paris-type arbuscular mycorrhyzae and vesicles, fistular stem, quadrangular in transverse section, with wings and hypostomatic cells with homogeneous mesophyll. The species of Calolisianthus show roots with Arum-type arbuscular mycorrhyzae and starch in the parenchymatic cells; quadrangular stem in transversal section, with wings and hypostomatic leaves, thick cuticle, homogenous mesophyll (excepting C. pendulus that presents dorsiventral leaves), sclereids and fibres associated to the midvein bundle, colleters in the leaf adaxial surface (interpectiolar region) and glandules at the leaf base. The glandules, present at the leaf base of C. pendulus and C. speciosus, also occur at the apex of the leaf and calyx of the three studied species and are extra-floral nectars (EFN). The EFN, at the leaf base and calyx of C. speciosus, secret considerable amount of nectar, which attracts ants. The EFN are comprised of secretory units the nectarioles consisted of 3-8 cells disposed in rosette with a mid channel. The inner periclinal walls and anticlinal ones opposed to the channel are thick and impregnated with lipid compounds. Isolate secretory unit nectariole can be observed along the leaf, on both surfaces, in C. amplissimus, C. pendulus, and C. speciosus. Colleters that secreted mucilage occur at the adaxial surface of the leaves base (intrapetiolar region) and at the calyx of the studied Calolisianthus species. The colleters of C. speciosus present short peduncle and multiseriate head formed by secretory cells, which are separated from the inner cells by a large apoplastic space where the mucilage is accumulated. The morphoanatomical characterization of Gentianaceaes species occurring in the Cerrado and campos rupestres points the rich structural diversity of herbaceous plants providing data that may contribute with the clarification of the taxonomical problems regarding this family to better identify the Deianira and Calolisianthus species and understand their adaptive strategies.

ASSUNTO(S)

campo rupestre anatomy campo rupestre botanica gentianaceae cerrado gentianaceae anatomia cerrado brazil

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