Developmental and Structural Section
Reginato, Marcelo , Boeger, Maria R.T. , Goldenberg, Renato .
Comparative anatomy of the vegetative organs in Pleiochiton A. Gray (Melastomataceae), with emphasis on adaptations to epiphytism.
Epiphytism is a widespread life form that evolved independently in several non-related plant taxa. Only few lineages have been able to occupy this epiphytic niche, probably due to the complex adaptive package that is necessary to live in it. Water scarcity is the main barrier limiting the survival of these plants, which is usually possible due to a vast array of characters and mechanisms that allow water storage. Melastomataceae is a family with 4500 species, most of them terrestrial herbs, shrubs or trees. Epiphytism apparently evolved only a few times in the family, mostly in the neotropical tribe Blakeeae and the old-world genera Medinilla and Pachycentria. In the neotropics, most epiphytes are found in the middle-altitude Andes and Colombian ChocÃ³, but a few occur along the Atlantic Coast in Eastern Brazil. The latter belong to Pleiochiton, a genus with 11 species, all endemic of Atlantic Forest, which most are very rare or at least poorly collected. In this study we present a comparative analysis on the anatomy of roots, shoots and leaves of three epiphytic species of Pleiochiton and a putative relative from Clidemia that is also an epiphyte. The four species share similar anatomical characters, suggesting adaptations toward water storage in all the structures and, consequently, to the water-limited epiphytic habitat. All four species present succulent roots with up to 75% of its volume with cells that store water. The leaves have about 50% of its volume with a hypodermis that also stores water, which are very similar to leaves of the epiphytic Peperomia and Gesneriaceae, suggesting evolutionary convergence. The leaf cells in all species have large vacuoles and compact mesophyll, with little intercellular spaces, all these usually related to CAM photosynthesis. The anatomical features found in all four species agree with previous phylogenetic analyses that show Clidemia blepharodes, P. ebracteatum and P. micranthum as members of a same clade.
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1 - The New York Botanical Garden, 200th St. & Southern Blvd., Bronx, NY, 10458-5126, USA
2 - Universidade Federal do Paraná, Departamento de Botanica, Campus Centro Politécnico , Caixa Postal 19031, Curitiba, PR, 81531970 , Brazil
Presentation Type: Oral Paper:Papers for Sections
Location: 555B/Convention Center
Date: Wednesday, August 4th, 2010
Time: 8:45 AM