1. Pistil length Sporophytic (2n) Stamen length Sporophytic (2n) Ovules within pistil Contain gametophytic stages (n) RESULTS Determining the relationship between the stamen and pistil length relative to megasporangial stages of Arabidopsis thaliana (L.) Heynh Columbia Ecotype Smith, B. and A.Hughes Department of Biological Sciences, York College of Pennsylvania INTRODUCTION A. thaliana has become a model organism for many plant studies (Smith, B. and J. Stum 2005). This project measured the length of the pistil and stamen, both sporophytic (2N) structures and compare those lengths to the selected stages of the embedded megagametophytic stages (N) of the ovule. A correlation between pistil length and the megagametophytic stages has been established (Bowman, 1997). It appears, without statistical analysis, that a direct correlation exists between the haploid stages within the ovule compared to the diploid stamen. The significance of this work is that haploid stages of the ovule that had been compared with previously measured pistil lengths now allows those pistil lengths to be compared to the stamen lengths we measured. Thus both pistil length and stamen length correlated with haploid stages in the ovule. This will benefit studies of haploid components of the more than 700 known ecotypes. The purpose of this investigation is to compare those sporophytic and gametophytic stages of the ovule with the measured stamen lengths and statistically determine the relationship that exists between sporophytic stamen length and the reported pistil lengths for those same stages. MATERIALS AND METHODS A. thaliana Columbia Ecotype was planted and whole inflorescences were collected and fixed in FPA 50 for minimum of 24 hours. Stored in 70% ETOH until cleared in Herr Clearing Fluid (Herr 1971). Floral buds were dissected while in Herr Fluid and whole stamens and pistils were removed. The stamens and pistils were measured and those measurements were compared to the selected megagametophytic stages. (see Table 1, p. 300 Bowman, 1994). Selected pistil sizes were compared to those in Bowman’s Table and stamens were measured before pistil was dissected to determine the megagametophytic size. These comparisons were recorded and the stage was confirmed. All work was performed using a Nikon SMZ1000 dissecting scope, and a Nikon eclipse 80i equipped with phase contrast objectives. Images were captured using a Nikon DXM 1200 F Digital Camera and measurements were made using Eclipsenet 1.16.5 software. Fig. 1. Mean stamen length (mm) relative to megasporophytic stages of A. thaliana DISCUSSION Comparisons can be made between the pistil length and the megagametic stage contained within. Pistil length measurements correlate with measured stamen lengths. Now, since correlation between pistil length and megagametophytic stage had already been shown we have yet another sporophytic marker, the stamen length, to use (Bowman, 1997). The mean stamen lengths were determined for each megagametophytic stage contained within the pistil (Fig. 1). The standard deviation of each stage was < 0.17 suggesting a very small standard deviation between the lengths of the stamens. A Pearson correlation analysis was performed to compare stamen length to pistil length. The r- value was determined to be 0.9896 indicating a strong correlation. The p-value was determined to be <.0001 which indicated the results to be significant. There had already been a correlation between pistil length and megagametophytic stage. This work indicates a correlation between pistil length and stamen length thus we can now infer a correlation between stamen length and megagametophytic stage. This study will make it much easier to obtain the haploid megagametophytic stages needed for studies of the female haploid of the many ecotypes found throughout the world. PURPOSE Our purpose was to find a rapid method for determining selected megagametophytic stages residing in the ovule of the pistil of the flower. Thus, prior to dissection, one could know the megagametophytic stages so that assessment of sizes of stages could be compared more quickly. Fig. 2. The correlation between pistil length and stamen length had an r-value of 0.9896 and a p-value of < 0.0001. LITERATURE CITED Bowman, John. 1997. Arabidopsis an Atlas of Morphology and Development. New York: Springer-Verlag, 1997. 299-313. Smith, B., and J. Stum. 2005. Comparison of Selected Stages of Megasporogenesis and Megagametogenesis in A. thaliana (L.) Heynh Landsberg erecta and Columbia Ecotypes. Abstracts Scientific Meeting, No. 129 Botany 2005, Austin TX Herr, J., Jr. 1971. A new clearing squash technique for the study of ovule development in angiosperms, Am.J.Bot. 58: 785-790.