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Abstract Detail



Systematics Section/ASPT

Ahedor, Adjoa [1].

Taxonomic Significance of Seed Morphology in the Genus Stemodia, Subfamily Gratioloideae (Plantaginaceae).

Seeds of members of subfamily Gratioloideae of family Plantaginaceae are small (less than 1 mm in length) with intricate surface sculpturing. Recent scanning electron microscopy (SEM) investigations of seeds of the subfamily revealed taxonomic significance in surface pattern variations. Stemodia is a pantropical genus; it comprises about 49 species distributed worldwide, with about 29 species occurring in Central and South America. Most of the species of genus are annuals, perennial herbs or small shrubs. Taxonomic placement of the genus in an appropriate tribe remains ambiguous; some authors have placed the genus under tribe Gratioleae whereas, others have placed it under tribe Stemodieae. Previous taxonomic studies of the seed of some New World species using light microscopy and later SEM studies revealed variation in seed morphology. The current study employed SEM to further evaluate seed surface variations in the genus. Seeds of 21 species sampled from North and South America, Oceania, Africa and Asia were examined. The investigations identified at least 9 seed types based on radial and tangential wall reliefs caused primarily by differential elongations, collapse and ornamentation of epidermal cells. The seed types identified were variations of reticulate, sulcate and granulate seed types. A few of the reticulate seed types shared similarity with seed types of some members of tribe Gratioleae whereas, the sulcate and granulate seed types were unique to the genus. Seed types were not unique to species distributed in any particular geographic region or hemisphere. The identification of varied seed types in a single genus suggests complexity among species and corroborates the current ambiguity in the appropriate taxonomic placement of the genus Stemodia in a tribe.

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1 - Rose State College, Life Science, 6420 S.E. 15th Street, Midwest City, OK, 73110, USA

Keywords:
Stemodia
Stemodieae
Gratioleae
SEM
Seed Types
Plantaginaceae.

Presentation Type: Oral Paper:Papers for Sections
Session: 49
Location: Marlborough A/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 2:15 PM
Number: 49004
Abstract ID:168
Candidate for Awards:None


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