1. Does Seed Depth of Arabidopsis Affect Germination or the Ability to Breach an Agar Surface?
Morgan Hiler, Carrie Martin, and Hannah Leirmoe Wofford College, South Carolina
Introduction
Germination Results
Discussion
These results support the original hypothesis that the seeds planted in both conditions would germinate; however, those seeds planted beneath the agar domes generally did not break the surface. Therefore, in the natural habitat of the Arabidopsis, if the seeds are planted rather than wind distributed the seeds may not be able to survive. This is because the seeds may not have enough stored energy to support the plant long enough for the shoot to break the surface.
The seedlings that emerged from the dome’s surface had been inadvertently displaced, and therefore had a shorter distance to grow to breach the surface. The seeds that were directly beneath the center of the domes did not reach the surface.
These results suggest that if the experiment had continued the plants may have eventually broken the agar surface, or died due to insufficient gas exchange. Our plants did not die in two weeks because unlike soil, agar is clear and the seeds may have been able to carry on photosynthesis whereas in soil they could not. The agar also allows for the shoots to respond to phototropism from the fluorescent lights rather than just geotropism, which is all the seeds could respond to if planted below the surface of soil.
Of the 42 seeds planted beneath the domes of agar 7 failed to germinate, and of the 42 seeds planted on top of the agar 7 also failed to germinate.
There was no significant difference in the germination rates in either treatment (P-value= 1, Fisher’s Exact Test).
Arabidopsis seeds are wind distributed; they germinate and grow where they land in the surface of soil. In the laboratory to facilitate the measurement of shoot and root growth the seeds are placed on agar. As far as we know there have been no previous experimentation to determine if the seeds of Arabidopsis grow when planted beneath the surface of agar.
Shoot Emergence Results
Hypothesis
Seed Placement
Arabidopsis seeds will germinate as well under the agar as on top of the agar.
The shoots of the Arabidopsis seeds planted beneath the agar will not break the surface.
Week 2 Shoot Growth
Of the forty-two seeds that were planted beneath the domes of agar four breached the surface. The other seeds grew sideways between the bottom of the agar dome and the top of the agar in the Petri dish. The shoots were beginning to grow leaves, but they were not able to grow straight up through the agar.
Methods
Experiment Procedure:
1. Each of the 14 seeds, Ecotype Columbia Arabidopsis, spaced evenly across the surface of six Petri dishes filled with 25mL solidified 0.8% agar.
2. Make 42 domes, approximately ½ in in diameter, with 0.8% agar on a flat.
3. Allow domes a few minuets to solidify, then place them on top of seven seeds in each Petri dish.
4. Seal dishes and placed them under florescent lights for a 16 hrs light and 8 hrs dark cycle.
5. After a week check seeds with a dissecting microscope for germination.
6. After two weeks check seeds again with the dissecting microscope for germination, and if any shoots have breached the surface of the agar.
References
Weigel, D. & J. Glazebrook. Arabidopsis: A Laboratory Manual Cold Spring Laboratory Press.
Acknowledgements
Thanks to Professors Davis and Abercrombie for their
support, suggestions, and help with statistical analysis.
Thanks also to T. Player and A. Steadman for their helpful comments.