Developmental and Structural Section
Armaiz, Gustavo , Peña, Jose , Ross, Robert .
Initiation of the Floral Organs of Melocactus intortus.
INITIATION of the floral organs of Melocactus intortus was compared to three previously studied genera of the Cactaceae- Pereskia, Opuntia, and Echinocereus. M. intortus shows a receptacle cup with centripetal tepals, centrifugal stamens, and a whorl of carpels. SEM and histological images reveal that numerous tepals are initiated certripetally as a peripheral meristem changes the young dome-shaped meristem into a floral cup. Two concentric whorls of stamens (8-10) and carpels (4-5) appear within the cup. Stamens are initiated centrifugally until these are adjacent to tepal primordia. The tips of the carpel primordia develop into stigma lobes which are carried upward by a ring meristem forming the style. Ovary walls are lined by carpel tissue with the residual floral meristem on the ovary floor. Taxonomists have historically viewed the terminal red cephalium of the Turks Cap group as evidence that this group is a highly derived section. Floral development, especially the precocious invagination of the receptacle prior to stamen and carpel initiation, is consistent with this interpretation. Funded by NIH GM59429.
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1 - Univ. of Puerto Rico-Cayey, Biology, 205 Barcelo Av., Cayey, PR, 00736, USA
Presentation Type: Poster:Posters for Sections
Location: Auditorium/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 12:30 PM