Developmental and Structural Section
Hodge, John , Kellogg, Elizabeth .
Inflorescence development of three species in the tribe Andropogoneae (Poaceae).
Andropogon gerardii (big bluestem), A.virginicus (broomsedge), and Schizachyriumscoparium (little bluestem) are easily distinguished at maturity despite the fact that they are all members of the tribe Andropogoneae, subtribe Andropogoninae. In order to determine when and how these distinctive morphological differences arise, inflorescences of the three were studied throughout their development. Images were taken of inflorescences by scanning electron microscopy (SEM) at various developmental stages; measurements were taken using ImageJ to quantify the morphological changes. Rachis branch length, spikelet pair (lateral branch) number on each rachis branch, spikelet length, lemma length, palea length, awn length, and samples of hair length were recorded. As expected, the size of these tissues varies between species. In addition allometric patterns of growth were noted in structures such as glumes in relation to spikelet length. Lateral branches of S.scoparium initiate and differentiate early relative to A. gerardii and A. virginicus, whereas unicellular hairs and awns develop early in A. virginicus in relation to A.gerardii and S. scoparium. Spikelet pairs form on one side of the rachisin A. gerardii, making the branches notably dorsi-ventral; this pattern appears in early development in A. virginicus but is much less prominentat maturity. Visible ridges marked the disarticulation zone in S. scoparium but were absent in both species of Andropogon. Some of the patterns visible in mature forms,such as rachis and lateral branch number and the general structure of lateral branches, appear at the earliest stages of development, where as other traitssuch as spikelet characteristics and identities (such as the undifferentiated pedicellate spikelets in A. virginicus)arise much later.
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1 - University of Missouri-St. Louis, Biology, One University Boulevard, St. Louis, MO, 63121, USA
2 - University of Missouri-St. Louis, Department of Biology, One University Boulevard, St. Louis, MO, 63121-4399, USA
Presentation Type: Poster:Posters for Sections
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM