Developmental and Structural Section
Ross, Robert , Armaiz, Gustavo .
Formation of Cephalium & Floral Organs in Melocactus intortus.
The cephalium of Melocactus intortus has been examined from leaf initiation through early flower development. Melocactus cephalia have rarely been studied using SEM techniques. Standard histological and SEM techniques were used on dissected cephalia. The mature cephalium meristem is about one mm wide and rests within a depression five mm across filled with uniserrate trichomes. Spirals of 20-25 leaf primordia arise from the flattened meristem. Leaves are shifted from growing horizontally to a vertical position by a leaf base and reach a length of 120 microns. On the adaxial surface of each leaf base an axillary bud expands and produces three to five spines acropetally. Encircled by trichomes and thin bristles the residual areole meristem becomes a floral meristem on a short receptacle. Therefore, cephalium areoles are monomorphic as in most Cactaceae. Initially the floral meristem is convex but flattens and forms a shallow concave surface 300 microns wide with tepal primordia around the upper perimeter. A peripheral meristem forms an inner cup 150 micrometer wide. Stamen primordia are formed on the lip of the cup and 5-6 carpel primordia arise on the cup walls. Additional stamens arise centrifugally until they reach the tepal primordia. Field observations, along with histological and SEM images are included. 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: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM