Arabidopsis thaliana (L.) Heynh.: Studying the relationship between the pedicel length and the pistil length in terms of the stages in the ovules. Tara Muse Department of Biological Sciences, York College of Pennsylvania Introduction - A. thaliana is a member of the mustard (Brassicaceae) family, which includes cultivated species such as cabbage and radish. - A rapid life cycle (about 6 weeks from germination to mature seed). (Bowman, 1994) Megasporogenesis (Describing stages of meiosis): -Megaspore Mother Cell (MMC)- Develops from a diploid cell in ovule’s nucellus. -Dyad- Prior to Meiosis II. Look for the size and shape of the dyad cells as they divide from the MMC. - Tetrad- Look for the arrangement and size of megaspores and the position of the functional spore. The cell on the chalazal end is the successful gametophyte and starts to divide to form the functional spore. (Herr, 1967) Megagametogenesis (Describing stages of haploid): -Functional Chalazal Spore- Look for the position of the nucleus. 1-nucleate embryo sac. -2-nucleate, 4-nucleate, and 8-nucleate- Look for position of nuclei and whether the integuments have grown around the nucellus or are just exhibiting growth around the nucellus. (Herr, 1967) Objectives In order to know the megasporogenetic and megagametogenic stages of the ovules of a particular flower in a whole inflorescence by comparing pedicel and pistil length. To make it easier and quicker to obtain quantitative information about the haploid portion of a dicot’s life history. All of this for the purpose of compiling information not available to morphologists or systematists. Planted 16 wells with 4 plants per well Inflorescence harvested and placed in FPA 50 for 24 hours, then stored in 70% ethanol for a week Inflorescence was transferred every 10 min starting with 80% ethanol up 100%. Stored in Herr fluid Pedicels measured in mm under dissecting scope Methods Flowers were dissected by removing sepals and petals. Pistil was measured in mm Stages of ovules found under microscope in megagametogenesis and megasporogenesis Statistical analysis done to compare length of pistil and pedicel to stages in ovules Overall Conclusions 1.My pistil length averages fell within the range of pistil length for various stages cited by Bowman (1994) 2. Now the pedicel length can be used in place of the pistil length when looking for the stages of the ovules. (Great savings in time). 3. Only measuring the pedicel length will make finding each stage of the ovules quicker and easier. Acknowledgements I would like to thank Dr. Smith for all of his time and help on this project. Results - Pistil lengths I measured fall between the ranges of the pistil lengths from the literature for each stage of the ovules (Table 1). - My pistil and pedicel length measurements show a very strong correlation (r² =0.9645) (Figure 1). Literature Cited Bowman, John Arabidopsis: An atlas of Morphology and Development. Springer-Verlag New York Inc., New York, NY. Bowman, John Arabidopsis: An atlas of Morphology and Development. Springer-Verlag New York Inc., New York, NY. Herr, J.M., Jr A new clearing squash technique for the study of ovule development in angiosperms. American Journal of Botany. 58: Herr, J.M., Jr A new clearing squash technique for the study of ovule development in angiosperms. American Journal of Botany. 58: