Anatomia de espécies brasileiras de Eriocaulaceae: Comanthera e Syngonanthus
Data
2016-01-08
Autores
Dugarte, Blanca Auxiliadora Corredor [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Dentre as Eriocaulaceae (sempre-vivas) brasileiras, alguns representantes de Comanthera e Syngonanthus são os mais comercializados e utilizados na ornamentação e constam da lista brasileira de espécies ameaçadas de extinção. Essas plantas crescem nos campos rupestres, sob situações climáticas adversas. Estudos taxonômicos e filogenéticos de Comanthera subg. Comanthera indicam falta de dados para maior suporte ao subgênero e nomeiam clados na distribuição das espécies. Procurando auxiliar a taxonomia e filogenia do grupo, bem como interpretar as adaptações ao ambiente e fornecer dados para futuro manejo, estudou-se aspectos da morfologia e anatomia de 24 espécies de Comanthera (envolvendo as espécies do clado “V”, “U” e “X”) e de Syngonanthus nitens. As espécies do clado “V”: Comanthera brasiliana, C. brunnea, C. caespitosa, C. magnifica e C. suberosa apresentam germinação e desenvolvimento pós-seminal mais rápido (< 7 dias) do que as demais Eriocaulaceae, e crescem em solo quartzítico pobre em nutrientes, cuja água escoa rápido. Apresentam envoltório seminal com projeções da endotesta com formas diferentes que são úteis para separar as espécies. O levantamento de estruturas anatômicas de folhas e escapos dessas espécies como: tipo de câmara subestomática, estrutura da margem foliar e número de feixes vasculares indicam agrupamentos entre elas e servirão para a sustentação do clado filogenético em que estão inseridas. Estruturas anatômicas como: presença de células de paredes espessadas, de hipoderme e parênquima clorofiliano compacto são respostas adaptativas à escassez hídrica, ventos fortes e radiação excessiva, presentes nos campos rupestres. As espécies de Comanthera subg. Comanthera que ocorrem na Bahia (nove espécies - clado “X”) e Minas Gerais (10 espécies - clado “U”) apresentam estruturas anatômicas de folhas e escapos como: células epidérmicas de paredes espessadas, estômatos com câmaras subestomáticas simples e presença de hipoderme, com similaridade alta, que é interpretada como resposta adaptativa às condições ambientais e não refletem relações de parentesco entre elas. Para Syngonanthus nitens (capim-dourado), comprimento e espessura de folhas e escapos; espessura das paredes das células epidérmicas, quantidade de camadas de células da hipoderme e tipo de parênquima clorofiliano definem os morfotipos “douradinho” e “douradão” utilizados no artesanato do Jalapão-TO. A maior quantidade de colênquima do que de esclerênquima no córtex do escapo do morfotipo “douradão” torna-o mais flexível e é usado na confecção de peças maiores (cestos, bolsas, etc.). Raízes com córtex que acumulam ar, epiderme e hipoderme foliares constituídas por células de paredes finas e mesofilo frouxo são respostas adaptativas dos morfotipos ao solo encharcado onde crescem.
Among the Brazilian Eriocaulaceae (sempre-vivas), the species most widely commercialized and used for decoration belong to Comanthera and Syngonanthus, and are already on the Brazilian list of endangered species. These plants grow in upland "campo rupestre" vegetation, under adverse climatic conditions. Taxonomic and phylogenetic studies of Comanthera subg. Comanthera have revealed a lack support for the subgenus and have used clades instead for discussing species distributions. The present study aimed to contribute to the taxonomy and phylogeny of the group, clarify environmental adaptations and provide data for future environmental management of natural populations. Morphological and anatomical features of 24 species of Comanthera (involving species of clades “V”, “U” and “X”) and of Syngonanthus nitens were studied. Species of clade “V” Comanthera brasiliana, C. brunnea, C. caespitosa, C. magnifica and C. suberosa exhibit more rapid germination and post-seminal development (< 7 days) than other Eriocaulaceae, and grow in nutrient-poor quartzite soils with rapid water drainage. They have seed coats with endotestal projections of differing shapes that are useful for separating the species. The survey of anatomical structures of the leaves and scapes of these species, such as the type of substomatal chamber, leaf margin structure and number of vascular bundles, revealed groupings that will serve to support the phylogenetic clade in which they are included. Anatomical structures such as presence of thick cell walls, hypodermis and compact chlorenchyma are important adaptive responses to the water scarcity, strong winds, and excessive radiation prevalent in "campo rupestre" habitats. The species of Comanthera subg. Comanthera that occur in Bahia (nine species – clade “X”) and Minas Gerais (10 species – clade “U”), have very similar anatomical leaf and scape structures, such as thick epidermal cell walls, stomata with simple substomatal chambers and the presence of a hypodermis. This similarity is interpreted as an adaptive response to environmental conditions and not as an indication of their phylogenetic relationship. For Syngonanthus nitens (capim-dourado, or “golden grass”), length and thickness of leaves and scapes, thickness of epidermal cell walls, number of hypodermis cell layers and type of chlorenchyma define the “douradinho” and “douradão” morphotypes used by artesans to make craft products in Jalapão, Tocantins state. The larger proportion of collenchyma than sclerenchyma in the cortex of the scape of the “douradão” morphotype makes it more flexible and useful for larger craftwork, such as baskets and bags. Roots with a cortex that accumulates air, leaf epidermis and hypodermis with thin cell walls and lax mesophyll are adaptive responses of the morphotypes to the waterlogged soil in which they grow.
Among the Brazilian Eriocaulaceae (sempre-vivas), the species most widely commercialized and used for decoration belong to Comanthera and Syngonanthus, and are already on the Brazilian list of endangered species. These plants grow in upland "campo rupestre" vegetation, under adverse climatic conditions. Taxonomic and phylogenetic studies of Comanthera subg. Comanthera have revealed a lack support for the subgenus and have used clades instead for discussing species distributions. The present study aimed to contribute to the taxonomy and phylogeny of the group, clarify environmental adaptations and provide data for future environmental management of natural populations. Morphological and anatomical features of 24 species of Comanthera (involving species of clades “V”, “U” and “X”) and of Syngonanthus nitens were studied. Species of clade “V” Comanthera brasiliana, C. brunnea, C. caespitosa, C. magnifica and C. suberosa exhibit more rapid germination and post-seminal development (< 7 days) than other Eriocaulaceae, and grow in nutrient-poor quartzite soils with rapid water drainage. They have seed coats with endotestal projections of differing shapes that are useful for separating the species. The survey of anatomical structures of the leaves and scapes of these species, such as the type of substomatal chamber, leaf margin structure and number of vascular bundles, revealed groupings that will serve to support the phylogenetic clade in which they are included. Anatomical structures such as presence of thick cell walls, hypodermis and compact chlorenchyma are important adaptive responses to the water scarcity, strong winds, and excessive radiation prevalent in "campo rupestre" habitats. The species of Comanthera subg. Comanthera that occur in Bahia (nine species – clade “X”) and Minas Gerais (10 species – clade “U”), have very similar anatomical leaf and scape structures, such as thick epidermal cell walls, stomata with simple substomatal chambers and the presence of a hypodermis. This similarity is interpreted as an adaptive response to environmental conditions and not as an indication of their phylogenetic relationship. For Syngonanthus nitens (capim-dourado, or “golden grass”), length and thickness of leaves and scapes, thickness of epidermal cell walls, number of hypodermis cell layers and type of chlorenchyma define the “douradinho” and “douradão” morphotypes used by artesans to make craft products in Jalapão, Tocantins state. The larger proportion of collenchyma than sclerenchyma in the cortex of the scape of the “douradão” morphotype makes it more flexible and useful for larger craftwork, such as baskets and bags. Roots with a cortex that accumulates air, leaf epidermis and hypodermis with thin cell walls and lax mesophyll are adaptive responses of the morphotypes to the waterlogged soil in which they grow.
Descrição
Palavras-chave
Anatomia, Escapos, Folhas, Paepalanthoideae, Raízes, Anatomy, Leaves, Paepalanthoideae, Roots, Scapes