Developmental and Structural Section
Gonzalez, Favio , Pabon Mora, Natalia .
Tackling the structural homology of trifid spines in the holy thorn (Berberis sp.).
Berberis s. l. (including Mahonia and Mahoberberis, Berberidaceae: Ranunculales) consists of approximately 400 species distributed in highland areas of the Americas and Tropical Africa, c. 200 spp. in China and 2 spp. in Europe. In South America, the genus is an important component of the high mountain Andean flora. Its common name, holy thorn (in Spanish “uĂ±a de gato”), refers to the usually trifid, spiniform structures formed along the stem nodes, in an alternate arrangement. The homology of the trifid structures is controversial. They have been interpreted as modified leaves, or as having a dual origin from both the blade (central spine) and the stipules (lateral spines); less often, they have also been interpreted as transformed branches. Our results, based on the study of leaf development in Berberis, indicate that there are three distinct leaf types per node: (1) leaves modified into usually trifid spines spirally arranged in long shoots; (2) normal (laminar), expanded leaves densely arranged in short shoots; and (3) cataphylls protecting axillary buds. We demonstrate that lateral spines correspond to the leaf blade, and that stipules are additional protective, non- spiny structures, formed at the flanks of the basal portion of the sheat-like leaf-base. Normal, laminar leaves (not spiny except along their margins) also have stipules. Furthermore, an abscission zone is formed between the stipules and the petiolar region. The whole surface of the cataphyll resembles that of the stipules in the spiny and the expanded leaves, which indicates that the entire cataphyll has a stipular origin. The differential development of three distinct types of leaves per node is discussed in terms of the occurrence of heteroblasty and/or heterophylly in Berberidaceae.
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1 - Universidad Nacional de Colombia, Ap Ae 7495, Bogota, Colombia
2 - Graduate Center CUNY/ New York Botanical Garden, Plant Sciences, 200th St and Southern Blvd, Plant Research Laboratory, Bronx, NY, 10458, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Ballroom 3/Cliff Lodge - Level B
Date: Monday, July 27th, 2009
Time: 4:30 PM