Table 1. Fibonacci Sequence for Plant 4 from Kyoto City ecotype.

Ratio Division

Width: 15.59

Length: 48.65 3.120590122 1

64.24 1.320452210 2

112.89 1.757316314 3

177.13 1.569049517 4

290.02 1.637328516 5

467.15 1.610750983 6

757.17 1.620828428 7

1224.32 1.616968448 8

1981.49 1.618441257 9

3205.81 1.617878465 10

5187.30 1.618093399 11

8393.11 1.618011297 12

13580.41 1.618042656 13

21973.52 1.618030678 14

35553.93 1.618035253 15

57527.45 1.618033506 16

93081.38 1.618034173 17

150608.83 1.618033918 18

243690.21 1.618034016 19

394299.04 1.618033978 20

637989.25 1.618033993 21

1032288.29 1.618033987 22

1670277.54 1.618033989 23

2702565.83 1.618033989 24

4372843.37 1.618033989 25

A Quantitative Analysis of Megagametogenesis in Two Species of Arabidopsis thaliana.

Kasey SandersDepartment of Biological Sciences, York College of Pennsylvania

Introduction• Arabidopsis thaliana, a flowering plant found in the mustard

(Brassicaceae) family (Figure 1), is a widely used biological model due to its rapid life cycle and abundant seed production. It was the first plant to have its genome mapped and offers important advantages in genetic and molecular biology (ABRC, 2012).

• Ecotypes of Arabidopsis thaliana have shown variations in flowering in response to growing conditions. These variations affect development of the haploid generation which can be seen by conducting microscopic studies of this generation (Smith, 1973).

• Megagametogenesis is the development of the megaspore into the embryonic sac which occurs in four stages: the functional megaspore (FM), 2-Nucleate (2N), 4-Nucleate (4N), and 8-nucleate (8N) (Figure 2).

• Two Japan ecotypes were studied; one from Kyoto City (Northern) and one from Sapporo (Southern). Ecotypes from these two cities were chosen because they differ in climate, elevation, and growing conditions (Figure 3). Observations were made to see if these differences cause changes in the development of the haploid generation.

• The Fibonacci series is used to determine if the nucleus sizes of the ecotypes of study correspond with expected results for Arabidopsis thaliana by evaluating the mean length and width of the nucleus. For the ratio to be met the mean width must be 10-50.5% of the mean length of the nucleus (Herr, 1967).

• Phi (1.6180339) is referred to as the “golden ratio” because it is the ratio by which many things develop. This ratio was proven to be a defining characteristic of length and width of gametophyte stages (Mitchison, 1977).

• For many ecotypes the three-decimal Phi is encountered at the 11th division and the seven-decimal Phi at the 18th division. Encountering the “golden ratio” at a different division shows a difference in development (Herr, 1967).

Objective• Successfully grow two ecotypes of Arabidopsis

thaliana from Japan; one from Kyoto City (Northern) and one from Sapporro (Southern).

• Determine if differences are present between ecotypes by measuring mean length and width for stages of Megagametogenesis.

• Using the Fibonacci Sequence the ecotypes will compared to the golden ratio to observe differences.

Methods

Seeds were ordered, planted in individual

wells, and each well was assigned a number.

Flowers were collected and fixed in FPA50.

Dehydrated in series of EtOH

(70, 80, 85, 90, 95, 100%)

Stored in Herr Clearing Fluid for 24 hours.

Ovules dissected from pistil , stage

determined, and measurements taken using phase contrast

microscope.

Data was calculated using a Fibonacci

sequence.

HypothesisH: The four stages of megagametogenesis will meet the 3-decimal Phi at the 11th division and the 7-decimal Phi at the 18th division and there will be no difference between plants of the same ecotype.

H0: There will be a difference between the stages of megagametogenesis for the two ecotypes and the golden ratio Phi.

Conclusion

• The 3-decimal Phi was reached at the 11th division and the 7-decimal Phi was reached at the 18th division.

• This is what was expected and shows that the change in environments does not have a large enough effect on the haploid generation to cause differences in development.

Literature Cited

• ABRC. 2012. The Ohio State University. http://abrc.osu.edu/• Herr, J. 1967. “On the Nature of Variation.”

Phytomorphology, 17:200-207.• Mitchison, G.J. 1977. “Phyllotaxis and the Fibonacci Series.”

Science 196 (4287): 270-275.• Smith, Bruce B. 1973. "The Use of a New Clearing

Technique for the Study of Early Ovule Development, Megasporogenesis, and Megagametogenesis in Five Species of Cornus L." Amer.ican Journal of Botany 60(4): 322-38.

• Smith, B, B. 1975. “A Quantitative Analysis of the Megagametophyte of Five Species of Cornus L.” American Journal of Botany 62(4): 387-394.

AcknowledgementsI would like to thank Dr. Smith for his guidance and expertise throughout my project as well as my peers who assisted me along the way.

Figure 3. Map of Japan. Cities of study include Sapporro (Northern) and Kyoto City (Southern), Japan and are marked by large red spots on map.http://www.lonelyplanet.com/maps/asia/japan/

Table 2. Fibonacci sequence for Plant 9 from Sapporo ecotype.

Ratio DivisionWidth 13.74Length 40.71 2.962882096 1

54.45 1.337509211 2

95.16 1.747658402 3

149.61 1.572194199 4

244.77 1.636053740 5

394.38 1.611226866 6

639.15 1.620645063 7

1033.53 1.617038254 8

1672.68 1.618414560 9

2706.21 1.617888658 10

4378.89 1.618089505 11

7085.10 1.618012784 12

11463.99 1.618042088 13

18549.09 1.618030895 14

30013.08 1.618035170 15

48562.17 1.618033537 16

78575.25 1.618034161 17

127137.42 1.618033923 18

205712.67 1.618034014 19

332850.09 1.618033979 20

538562.76 1.618033992 21

871412.85 1.618033987 22

1409975.61 1.618033989 23

2281388.46 1.618033989 24

3691364.07 1.618033989 25

Figure 2. Stages of Megagametogenesis. This includes the functional megaspore, 2-Nucleate, 4-Nucleate, and 8-Nucleate.http://agritech.tnau.ac.in/seed/seedconcepts.html

Figure 1. Arabidopsis thaliana after flowering.http://commons.wikimedia.org/wiki/File:Arabidopsis_thaliana_inflorescencias.jpg

Results

A B

C DFigure 4. Images taken of the four stages of Megagametogenesis. Circles indicate location of nucleus. A) Functional Megaspore B) 2-Nucleate C) 4-Nucleate D)8-Nucleate.