Anatomy and ontogeny of the pericarp of Pterodon emarginatus Vogel (Fabaceae, Faboideae), with emphasis on secretory ducts
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Data
2008-09-01
Autores
Paiva, Élder A.S.
Oliveira, Denise M.T.
Machado, Silvia R. [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Academia Brasileira de Ciências
Resumo
Interpretações discrepantes e incompletas têm sido conferidas ao fruto de Pterodon, especialmente no que tange à determinação estrutural da porção pericárpica que acompanha a semente na dispersão. Assim, com o objetivo de dirimir tais dúvidas e analisar a organização ultra-estrutural das estruturas secretoras presentes no diásporo de Pterodon emarginatus, realizaram-se estudos convencionais aos microscópios de luz e eletrônico de transmissão. Nas fases iniciais de desenvolvimento do fruto, prevalecem divisões celulares; pela ação do meristema subadaxial e do adaxial, formam-se, respectivamente, o mesocarpo interno fibroso e o endocarpo composto por epiderme multisseriada. No mesocarpo mediano, entre os feixes vasculares laterais, diferenciam-se numerosos ductos secretores lisígenos. Após a lise das células centrais e formação do lume, os ductos apresentam epitélio secretor uniestratificado, com células densas; gotas de óleo são observadas no epitélio secretor e tecido subjacente. Na maturidade, o exocarpo unisseriado e o mesocarpo externo, ambos fenólicos, descamam irregularmente, sendo o diásporo constituído pela ala papirácea e quebradiça, ligada ao núcleo seminífero que abrange o mesocarpo mediano de células lignificadas, margeando feixes vasculares e muitos ductos secretores, que apresentam acúmulo de oleorresina e cujas células epiteliais tornam-se vacuoladas. O fruto de Pterodon emarginatus é, portanto, uma criptossâmara.
Discrepant and incomplete interpretations of fruits of Pterodon have been published, especially on the structural interpretation of the pericarp portion that remain attached to the seed upon dispersal. The present work clarified these doubts and analyzed ultrastructural aspects of the Pterodon emarginatus diaspores using light and transmission electron microscopes. Cell divisions are prevalent among the initial phases of development, and the subadaxial and adaxial meristems form the fibrous inner mesocarp and the endocarp composed of multi-seriate epidermis, respectively. At the median mesocarp, numerous secretory ducts differentiate between the lateral bundles, by lytic process. After lysis of the central cells and the formation of the lumen, the ducts show unistratified secretory epithelium with dense cells; oil droplets are observed on the secretory epithelium and the subadjacent tissues. At maturity, the uniseriate exocarp and the outer mesocarp slough off in an irregular fashion, leaving the diaspore composed of a papery and brittle wing linked to a seed chamber that includes the median mesocarp composed of lignified cells, bordering vascular bundles and many secretory ducts whose epithelial cells develop large vacuoles that accumulate oleoresins. The Pterodon emarginatus fruit is a cryptosamara.
Discrepant and incomplete interpretations of fruits of Pterodon have been published, especially on the structural interpretation of the pericarp portion that remain attached to the seed upon dispersal. The present work clarified these doubts and analyzed ultrastructural aspects of the Pterodon emarginatus diaspores using light and transmission electron microscopes. Cell divisions are prevalent among the initial phases of development, and the subadaxial and adaxial meristems form the fibrous inner mesocarp and the endocarp composed of multi-seriate epidermis, respectively. At the median mesocarp, numerous secretory ducts differentiate between the lateral bundles, by lytic process. After lysis of the central cells and the formation of the lumen, the ducts show unistratified secretory epithelium with dense cells; oil droplets are observed on the secretory epithelium and the subadjacent tissues. At maturity, the uniseriate exocarp and the outer mesocarp slough off in an irregular fashion, leaving the diaspore composed of a papery and brittle wing linked to a seed chamber that includes the median mesocarp composed of lignified cells, bordering vascular bundles and many secretory ducts whose epithelial cells develop large vacuoles that accumulate oleoresins. The Pterodon emarginatus fruit is a cryptosamara.
Descrição
Palavras-chave
Pterodon emarginatus, desenvolvimento, fruto, ducto secretor, resina, ultra-estrutura, Pterodon emarginatus, development, fruit, secretory duct, resin, ultrastructure
Como citar
Anais da Academia Brasileira de Ciências. Academia Brasileira de Ciências, v. 80, n. 3, p. 455-465, 2008.