19th Annual Student Research Conference
Science
Using Pollen Ontogeny in Ephedra to Evaluate the Anthophyte Hypothesis
Allison S. Doores
Dr. Jeffrey M. Osborn, Faculty Mentor
Ephedra, along with Welwitschia and Gnetum, comprise the gymnospermous order Gnetales. Historically, the order has been regarded as the sister group to flowering plants in a clade known as anthophytes; however, recent molecular studies have allied the Gnetales with conifers. The objective of this project was to comparatively study pollen ontogeny in Ephedra americana. Light, scanning electron, and transmission electron microscopy were used to document major developmental stages, including the microspore mother cell, tetrad, free microspore, and mature stages. Developmental events including the deposition of a callose wall, exine, foot layer, and endexine lamellae will be discussed. Significant exine deposition occurs during the tetrad stage, although compression of endexine lamellae continues during the free microspore stage. Mature pollen grains are ellipsoidal and are inaperturate. These developmental characters will be compared to those in conifers and angiosperms, and will be discussed regarding systematic and phylogenetic interpretations of Ephedra and Gnetales.
Keywords: pollen, botany, ontogeny, Gnetales, anthophytes, Ephedra
Topic(s):Biology
Presentation Type: Oral Paper
Session: 54-4
Location: VH 1412
Time: 3:30