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Abstract Detail


Developmental and Structural Section

Almeida, Odair J. G. [1], Paoli, Adelita A. S.  [2], Souza, Luiz A. [3], Cota-Sanchez, Hugo [4].

Post-seminal development and seedling structure in the epiphytic cactus Epiphyllum phyllanthus (L.) Haw. (Cactaceae).

Epiphyllum phyllanthus is a strict epiphytic cactus widely distributed throughout South America. It is the only Epiphyllum species native to Brazil. The species, for which limited information exists regarding the nature of its reproductive structures, is included on the Red List of the International Union for Conservation of Nature. The goals of this study were: 1) to analyse the morphological post-seminal development and 2) to conduct an anatomic study of the seedling of E. phyllanthus. The seeds were collected in the states of Paraná and São Paulo, Brazil, and grown at 25ºC. After germination, the seedlings were transferred to coconut fibre substrate, where the developmental stages were monitored during 210 days. Seeds and seedlings were fixed, processed, and analyzed using light and scanning electron microscopy. The seed has scarce storage material and is mostly filled with the curved embryo, rich in lipoproteins. Mucilage forms on the testa during germination. The seedling is epigeal-phanerocotyledonary. The tetrarch taproot has determinate growth; triarch/tetrarch adventitious roots arise in the collet region and on the base of the hypocotyl, which exhibits a transitional structure (from root to stem), a cortex with parenchyma cells, and a central cylinder with tracheary elements ordered in an annular shape and enclosing the pith. The vascular structure of the E. phyllanthus seedlings resembles that of Pereskia, Opuntia, Nopalea, and Cereus tortuosos. The sessile and photosynthetic cotyledons, which persist throughout seedling development, have a great amount of parenchyma and one midrib. The hypocotyl, cotyledons and phylloclade (epicotyl) are glabrous with uniseriate epidermis, thick cuticle, and parallelocytic stomata. Despite the epiphytic lifestyle, the E. phyllanthus seedlings show stronger morpho-anatomical similarity with basal terrestrial lineages, such as Pereskia, Opuntia, and Nopalea, rather than putatively apomorphic epiphytic species, such as Rhipsalis spp., which have diarch taproot and reduced cotyledons. Could this resemblance suggest the origin of epiphytic cacti from terrestrial ancestors?

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1 - University of Saskatchewan, Biology, 112 Science Place, Saskatoon, SK, S7N 5E2, Canada
2 - Universidade Estadual Paulista, Botnica, Av 24 A, 1515, Bela Vista, Rio Claro, SP, 13506-900, BRAZIL
3 - Universidade Estadual de Maring, Biologia, Av Colombo, 5790, Jardim Universitrio, Maring, PR, 87020-900, BRAZIL
4 - University of Saskatchewan, Biology, 112, Science Place , Saskatoon, SK, S7N 5E2, CANADA

Keywords:
anatomy
Cotyledons
mucilage
Transitional structure.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM
Number: PDS012
Abstract ID:660

Canceled

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