Estrutura foliar de Loudetiopsis chrysothrix (Nees) Conert e Tristachya leiostachya Nees (Poaceae)
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Data
2005-03-01
Autores
Alvarez, Juliana M [UNESP]
Rocha, Joecildo F [UNESP]
Machado, Silva R
Título da Revista
ISSN da Revista
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Editor
Sociedade Botânica de São Paulo
Resumo
Loudetiopsis chrysothrix e Tristachya leiostachya são espécies de gramíneas que apresentam grande similaridade morfológica, distinguindose pelo número de estames e pelas características da arista. Entretanto, tais estruturas são caducas e, freqüentemente, estão ausentes na espigueta madura o que dificulta a identificação. Visando reconhecer caracteres úteis na delimitação dessas espécies, neste trabalho foram estudadas a anatomia e a ultra-estrutura da lâmina foliar. Os caracteres diferenciais entre as duas espécies foram: disposição dos tricomas tipo espinho na superfície adaxial da lâmina; profundidade dos sulcos na superfície adaxial; formato das saliências nos feixes de primeira ordem; tamanho, posição e o arranjo dos feixes vasculares na lâmina foliar; contorno dos vasos de metaxilema; número de células da extensão da bainha dos feixes vasculares; presença/ausência de células incolores no mesofilo; número de estratos de células do clorênquima radiado e distribuição do esclerênquima subepidérmico. em ambas as espécies, os cloroplastos do clorênquima apresentam grana e ausência de grãos-de-amido; os da bainha são agranais, com ou sem grãos-de-amido. Outras características como a presença de ceras epicuticulares, estômatos alojados em sulcos na superfície adaxial, diferenças no grau de sinuosidade das paredes das células epidérmicas e na estrutura das paredes celulares são comuns a espécies de cerrados e podem estar relacionadas com a economia de água.
Loudetiopsis chrysothrix and Tristachya leiostachya are grasses species showing great morphological similarity, but differing in stamen number and awn characteristics. However, these structures are deciduous and frequently absent in the mature espikelet, which makes their identification difficult. In order to recognize useful characters for species delimitation, this paper studied the leaf blade anatomy and ultrastructure. The different characteristics between these species were: prickle hair arrangement on the leaf blade adaxial surface; furrow depth on the adaxial surface; saliency shape on the first order bundle; vascular bundle size, position, and arrangement on the leaf blade; metaxylem vessel outline; number of cells in the bundle sheath extension; presence/absence of colourless cells in the mesophyll; number of chlorenchyma radiated cell strata and distribution of the sub epidermal scherenchyma. In both species, chloroplasts of the chlorenchyma show grana and absence of starch grains; those in the sheath are agranal, with or without starch grains. Other characteristics such as presence of epicuticular waxes, stomata in furrows on the adaxial surface, differences in the sinuosity degree of the epidermal cell wall, and cell wall structure are common in cerrado species and can be related to water saving.
Loudetiopsis chrysothrix and Tristachya leiostachya are grasses species showing great morphological similarity, but differing in stamen number and awn characteristics. However, these structures are deciduous and frequently absent in the mature espikelet, which makes their identification difficult. In order to recognize useful characters for species delimitation, this paper studied the leaf blade anatomy and ultrastructure. The different characteristics between these species were: prickle hair arrangement on the leaf blade adaxial surface; furrow depth on the adaxial surface; saliency shape on the first order bundle; vascular bundle size, position, and arrangement on the leaf blade; metaxylem vessel outline; number of cells in the bundle sheath extension; presence/absence of colourless cells in the mesophyll; number of chlorenchyma radiated cell strata and distribution of the sub epidermal scherenchyma. In both species, chloroplasts of the chlorenchyma show grana and absence of starch grains; those in the sheath are agranal, with or without starch grains. Other characteristics such as presence of epicuticular waxes, stomata in furrows on the adaxial surface, differences in the sinuosity degree of the epidermal cell wall, and cell wall structure are common in cerrado species and can be related to water saving.
Descrição
Palavras-chave
cerrado, estrutura foliar, Loudetiopsis chrysothrix, Poaceae, Tristachya leiostachya, cerrado, leaf structure, Loudetiopsis chrysothrix, Poaceae, Tristachya leiostachya
Como citar
Brazilian Journal of Botany. Sociedade Botânica de São Paulo, v. 28, n. 1, p. 23-37, 2005.