1. Table 1. Bud and coinciding pistil lengths categorized by stage of embryo sac development. Stage of embryo sacPistil lengthBud length developmentª (mm) b (mm) c Megasporocyte0.550.69 Dyad0.750.93 Tetrad0.931.19 Functional Spore1.31.62 2-nucleate embryo sac1.591.82 4-nucleate embryo sac1.761.98 8-nucleate embryo sac1.952.06 ª Stages of embryo sac from table: M.C. Webb and J.L. Bowman (Bowman 1994). b Pistil lengths presented are the average of 10 pistils measured in each stage c Bud lengths presented are the average of 10 buds measured in each stage Identification of Ovule and Embryo Sac Developmental Stages using Coinciding Bud Length in Arabidopsis thaliana (L.) Heynh Columbia Ecotype Dillaha, A, and B. Smith Department of Biological Sciences, York College of Pennsylvania INTRODUCTION Nearly all aspects of flower development and morphology of A. thaliana have been characterized in detail (Herr 1967, Bowman 1994). However, current techniques for determining stage of embryo sac development remain tedious and time-consuming. This study thus seeks to speed the process of elucidating the stage of development of a particular ovule. The obvious significance of speeding this process is to allow for increased comparative gametophyte studies, which ultimately may allow for phylogenetic interpretation (Herr 1967, Smith 1975). In this study, bud lengths from A. thaliana Columbia ecotype were compared to both coinciding pistil lengths as well as stage of embryo sac development, as previously defined (Bowman 1994, See Table 1), in order to indirectly correlate bud size to stage of early flower development. This indirect correlation would permit the inference that bud size is correlated to the coinciding stage of embryo sac development, thereby allowing for faster screening of buds. METHODS  Plants grown in York College greenhouse  Inflorescences removed and fixed for minimum of 24 hr in FPA50  Inflorescences transferred to screwcap vials and stored in 70 % ethyl alcohol until use  Inflorescences dehydrated to 100% ethyl alcohol  Inflorescences cleared using Herr fluid  Bud length and coinciding pistil length measured  Ovules dissected from cleared ovularies  Microscopic examination to determine stage of embryo sac development RESULTS  Strong positive correlation between bud and coinciding pistil length (Pearson r value of.9910 and R² value of 0,9822). Figure 1. Mean bud and coinciding pistil lengths categorized by stage of embryo sac development. Error bars represent standard error of the mean. Figure 2. Correlation between Bud length and coinciding pistil length. Pearson correlation analysis was computed on means (r value of 0.9910). Acknowledgements: Dr. Rehnberg CONCLUSION  Strong correlation allows for the indirect correlation between bud length and stage of embryo sac development permitting faster screening of buds for future studies LEGEND A. Whole flower; B. Millimeter ruler; C. Cleared flower, A=anther, P=pistil; D. O=ovule; E. PL=placenta, O=ovule mm AB C DE P A O PL O Literature Cited Bowman, J. 1994. Arabidopsis-Springer Verlag, New York, NY. Herr, J. 1967. On the Nature of Variation. Phytomorphology, 17:200-207 Smith, B. A Quantitative Analysis of the Megagametopohyte of Five species of Cornus L. Amer. J. Bot. 62:387-394.