Analysis of Mean Length/Width of Megagametophytic Stages of Arabidopsis thaliana from Divergent Elevations Benjamin Doyle Department of Biological Sciences, York College of Pennsylvania Introduction Ecotypes of Arabidopsis thaliana have been shown to vary in flowering time in different climates and in response to environment. Variation in flowering may show differences in the haploid generation; specifically, size during megagametogenesis. Four stages of haploid growth during megagametogenesis are the functional megaspore (FM), 2-nucleate, 4-nucleate, and 8-nucleate stages. Two ecotypes with large differences in elevation were chosen. Urban town of Poppelsdorf, Germany (1.0m) with a fair and mild climate; and colder, mountainous terrain of Pitztal, Austria (1000m). The haploid generation of these ecotypes has never been studied. The “golden ratio” known as Phi ( ) has been proven as a distinguishing characteristic when comparing lengths and widths of gametophyte stages. The seventh- decimal ratio of Phi is reached by many ecotypes of Arabidopsis at the 18 th division. The Fibonacci series is used to relate the mean length/width of the measured stages to Phi and determine if there is a correlation. Mean width must be between % of the mean length for ratio to be met. Objectives  Successfully grow and harvest two ecotypes of A. thaliana.  Measure length and width for all four haploid stages during megagametogenesis.  Using mean length and width, determine if the haploid stages show a correlation to the golden ratio Phi at the 18 th division. Hypothesis H: All four stages of the haploid generation will show a positive correlation to the seventh-decimal ratio of Phi in both ecotypes of A. thaliana. H 0 : There will be no correlation between the haploid generations of the two ecotypes of A. thaliana and the seventh-decimal ratio of Phi. Methods To determine if the stages met the 18 division of Phi, the mean length and width were added in a Fibonacci series, then divided by the mean length after each new number in the series to ascertain at what division Phi ( ) would be reached. Fibonacci Series addition is expressed as F n = F n-1 +F n-2 Addition of the two prior numbers, beginning with mean length and width for each stage, yields the next number in the series. Each division is expressed as (W+L)/L, for a ratio. Results Literature Cited Bowman, John. Arabidopsis - An Atlas of Morphology and Development. New York: Springer-Verlag Inc, Print. Herr Jr., John M. "Investigations of Structural and Developmental Variation in Angiosperms: The Art and Science of Focused Effort." SE Biology 57.1 (2010): Print. Smith, Bruce B. "The Use of a New Clearing Technique for the Study of Early Ovule Development, Megasporogenesis, and Megagametogenesis in Five Species of Cornus L." Amer. J. Bot (1973): Print. Acknowledgements I would like to thank Dr. Smith for his expertise, guidance, and constant support throughout this project and the Biology Dept. curriculum. Additional thanks to students Dena Amato and Shane Lohss for research assistance. German (1.0m), Po-0 Mean WidthMean Length Functional Megaspore Nucleate Nucleate Nucleate Austria (1000m), Po-0 Mean WidthMean Length Functional Megaspore Nucleate Nucleate Nucleate Functional Megaspore 2-Nucleate 4-Nucleate 8-Nucleate Conclusions  All four stages of the haploid generation, for both ecotypes, met the requirements for the seventh-decimal ratio of Phi at the 17 th division.  Different from expected result of reaching at 18 th division.  Possible defining characteristic for these two specific ecotypes. Though shared, could distinguish them from numerous others.  Divergent elevation/environment was the variable, but cannot correlate results to these, as both ecotypes reached Phi at the same division.  Increasing significant difference between the mean length/width ratio when comparing the two ecotypes.  Possible result from the large difference in elevation and environment, but further research needed to test. Further Research There are over 800 different ecotypes of A. thaliana; the majority of which have not been studied for their haploid generation. These other ecotypes may be studied with the same methods and characterizing objective. Test the same ecotypes with a different variable, e.g. soil moisture or hours of growing light. Seeds of German and Austria ecotypes ordered Week-long vernalization for freeze-shock prior to growth Planted in individual wells with fertilizer Collected flowers and stored in FPA 50 Dehydrated in ETOH series ( %) and stored in Herr fluid Dissected and studied with phase-contrast microscope Measured 10 of each haploid stage per ecotype