Systematics Section / ASPT
Ahedor, Adjoa R. , Elisens, Wayne .
Taxonomic Significance of Seed Surface Sculpturing in the Subtribe Gratioliinae (Tribe Gratioleae - Plantaginaceae).
Seeds of most genera of subtribe Gratioliinae are small (less than 1 mm in length) and reticulate with intricate surface sculpturing. We employed scanning electron microscopy (SEM) to evaluate variation in testa surface patterns from 37 species representing 8 of 10 genera in the subtribe. Seed shapes were ovoid, ellipsoid or cylindroid. We identified 13 patterns of seeds based on surface sculpturing. Seeds of the genus Mecardonia had smooth tangential walls with two types of radial wall thickenings: nodulose and anodulose. Seeds of the genus Bacopa had low radial walls with four types of tangential wall surface patterns: alveolate, papillate, granulate and irregularly reticulate. The genus Gratiola had two main seed types: one type with alveolate patterns on both radial and tangential walls, and the other with corrugate tangential walls, which was similar to that observed for the segregate genus Sophronanthe. Two seed types were observed for the genus Scoparia: one type had high radial walls with rugulose tangential walls whereas the other type had low radial walls with rugose tangential walls. Seeds of the monotypic genus Amphianthus had moderately high radial walls with smooth tangential walls. This seed type was distinct for the genus. The genus Stemodia had two seed types. Seeds were either reticulate with rugulose tangential walls, or longitudinally striated with minutely spiculose patterns. Most genera had two or more unique seed types that were not shared with other genera. Seed surface sculpturing can therefore be used in characterizing the various genera of subtribe Gratioliinae. The distinct differences in seed morphology observed for Mecardonia and Bacopa support the segregation of Mecardonia from Bacopa. Similar seed types shared among species of Gratiola and the monotypic genus Sophronanthe, do not suggest recognition of Sophronanthe.
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1 - University of Oklahoma, Department of Botany and Microbiology, 770 Van Vleet Oval, Norman, Oklahoma, 73019, USA
2 - University of Oklahoma, Botany & Microbiology and Oklahoma Biological Survey, 770 Van Vleet Oval, Norman, Oklahoma, 73019, USA
Scanning Electron Microscopy.
Presentation Type: Oral Paper
Location: Salon G - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 4:15 PM