Transcript Morgan Hiler, Carrie Martin, and Hannah Leirmoe

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
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.
Germination Results
Discussion
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).
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.
Shoot Emergence Results
Hypothesis
Arabidopsis seeds will germinate as well under the
agar as on top of the agar.
Seed Placement
The shoots of the Arabidopsis seeds planted beneath
the agar will not break the surface.
Week 2 Shoot Growth
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.
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.
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.
References
Weigel, D. & J. Glazebrook. Arabidopsis: A Laboratory
Manual. 2002. 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.