Early Ovule development of Coronilla varia L. with a specific focus on megasporogenesis and megagametogenesis Justin Icenroad, Department of Biological Sciences, York College of Pennsylvania Coronilla varia, also known as Crown Vetch, is a common angiosperm and is part of the Fabaceae family. C. varia is often found along road sides from May to August and is popular in the United States for use in erosion control. In the early 1900’s, plant embryology became of interest of early botanist’s and was never really described (Johansen, 1945), but now using certain methodology, plant’s can be examined more rapidly and readily. In the nucellus of the ovule, a combination of two important processes happens to allow the plant to produce an egg, one is megasporogenesis, and the other is megagametogenesis. Megasporogenesis is the process of a diploid megaspore mother cell to undergo meiosis to produce four haploid cells. The chalazal cell usually becomes the megasporocyte giving rise to the process of megagametogenesis. Megagametogenesis involves the megasporocyte going through mitosis three times to produce eight nuclei. (see figure upper right hand corner) Since early ovule studies are not commonly performed, the information gained from studies such as these are not available for angiosperms phylogenetic studies. (Smith, 1973) Introduction Objectives To examine C. varia and record each stage of megasporogenesis (meiosis) and megagametogenesis(mitosis) with photography and compare to previous research of angiosperms. Methodology Coronilla varia was found and flowers were removed with forceps. Dehydration steps – FPA 50 -> to 70% EtOH and in 5% increments for 15 minutes each, up to 100% EtOH for total removal of water. C. varia were placed into Herr fluid, a new method compared to serial sectioning. To start study of megasporogenesis (meiosis stages), remove smallest flower possible to examine. Using a NIKON SMZ 1000 dissecting microscope, perianth parts removed to expose the sexual structures i.e., gynoecium and androecium Gynoecial structure (female) is located behind androecial structures or stamens (male). Carefully, push aside stamens and remove ovary from this hypogenous flower. Ovary dissected to remove ovules Ovules placed on Raj slide with Herr fluid and covered with cover slip. Slide taken to NIKON Eclipse 80i microscope with phase contrast objectives and viewed at 1000 X. Images captured using a NIKON digital camera DXM 1200 F and saved to files using NIKON NIS-Elements D software MMC Results Megasporogenesis Stages Dyad Tetrad Megagametogenesis Stages 2-Nucleate 4-Nucleate Results contd. 8-Nucleate Acknowledgements I would like to give special thanks to Dr. Bruce Smith for assisting me with this project throughout the summer/fall of 2010, and to the entire biology faculty for sharing their knowledge these past four years. Overall Conclusions Megasprogenesis and megagametogenesis is now known for a Fabaceae species not studied in the past. This adds new data that may benefit phylogenetic studies within the Fabaceae. Literature Cited Smith, B.B The use of a new clearing technique for the study of early ovule development, megasprogenesis, and megagametogenesis in five species of Cornus L. Am J of Bot. Vol 60, Number 4