2008 Alaska Park Science Symposium
October 14, 2008
Comparative study of seed coat micromorphology and seed anatomy in Alaskan Oxytropis (Loco-weed, Fabaceae) using SEM, and their Taxonomic Significance
Rose Farrington1, Zachary J Meyers2, Steffi Ickert-Bond3
1UAF Biology and Wildlife / Museum of the North, Fairbanks, AK, 99775, USA, rosie101986@hotmail.com
2UAF Biology and Wildlife / Museum of the North, Fairbanks, AK, 99775, USA, ZJMEYERS85@gmail.com
3IAB / Museum of the North, Fairbanks, AK, 99775, USA, ffsi1@uaf.edu
Oxytropis (loco-weed, Fabaceae) are typical members of the Arctic flora and include 20
species in Alaska occurring in a wide range of habitats (e.g. forest, meadow, tundra) with
some species being narrow endemics. Botanists in Alaska have long noticed a high degree of morphological variation within well-established taxa. This has resulted in taxonomic controversy and species delimitation in Oxytropis is in need of further study. This project seeks to determine differences in surface features and anatomy of seeds of ca. 13 species of Oxytropis (loco-weed, Fabaceae) that occur in Alaska. The study is based on dry herbarium specimens from the University of Alaska Museum Herbarium (ALA). Observations made using scanning electron microscopy indicate that seed surface micromorphology is primarily rugulate, with either 1) tightly interwoven thin rugae, 2) thick rugae, or 3) thick raised primary and thin recessed secondary rugae. For anatomical studies, dry seeds were rehydrated in equal parts of glycerol, water and ethanol and then sectioned by hand. The seed coat in Oxytropis is well differentiated and exotestal with the outer integument providing the mechanical layer of the seed. A uniseriate epidermis is covered by a cuticle on upper anticlinal walls. The subepidermal layer is composed of single layer of prominent macrosclereids, followed by a single row of osteosclereids and 5-8 rows of compressed tangentially elongate parenchyma cells of the nucellus. The taxonomic utility of micromorphological and anatomical characters in Alaskan Oxytropis seeds is demonstrated and a key is provided.
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