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Control of Seed Germination in Plants
Livia Büchel, Supervision: Hicham Chahtane, UNIGE
Introduction
Seeds are a crucial element of almost every terrestrial plant. This
protective structure containing the embryo is highly sensible to its
environment. If the conditions are adequate it carefully opens its coat,
begins to germinate and develops into a fragile seedling. Parameters such
as light and temperature play a big role in this metabolic state. Also other
components like bacteria can have an immense impact on the seed and
modify its developmental stages and germination rate. Understanding how
seeds germinate and what factors they’re affected by is an important
scientifical question. Taking Arabiodopsis thaliana as a model we have
tested how biotic and abiotic factors can impact seed germination in this
species.
Methods and Materials
For the entire project the seeds of Arabidopsis thaliana have been used. It
is a popular plant in many laboratories because of its fast growth rate, low
price and the simple ways to cultivate it. Sterilisation of seeds is the first
and crucial step before the seed germination experiment can be started. It
assures that there are no bacteria or other pollution around the seeds.
Some seeds have been taken and put into a tube. After that four washing
processes take place. The first of them with 1ml of a 30% bleach solution
and the three others with water in steril conditions to avoid contamination.
Each process has a duration of 10 minutes. After that small amounts of
seeds are put on a sterile medium plate with the use of pipettes.
We prepared multiple of the petridishes with seeds and exposed them
under different conditions:
•
•
•
•
With sunlight, 23°C
Without light, 23°C
With sunlight, 32 °C
With sunlight, 10 °C
•
•
With small amount of bacteria
Control (without bacteria)
Impacts of light and temperature
Impact of bacteria
After a certain amount of time we examinated our seeds with binocular to
see how far the germination has progressed.
Results
Experiment 1:
After controlling the seed germination of Arabidopsis thaliana exposed to
bacteria for more than 70 hours we can see that the seeds that are in the
control without bacteria germinated normally and little leafs already came
out of its capsule (Figure 1). The seeds in the petridish, which contains
bacteria, didn’t come as far with their development. The seeds with 3 cm
distance to the bacteria didn’t even start to make leafs. Where the
distance with 6 cm is a little bigger the seeds show a small amount of
germination.
2h
48h
70h
Control
3 cm
distance
to
bacteria
6 cm
distance
to
bacteria
Figure 1 : Effect of bacteria in seed germination of Arabidopsis
thaliana.
Experiment 2:
To see if abiotic factors can have an effect on seed germination, I tested
the impact of light, low and high temperature on these process (Figure 2).
Comparing the seeds which were exposed to 32°C and sunlight with the
control shows that less seeds started to germinate there. At 10°C and
sunlight developmental changes are visible. Whereas we can see that with
23°C and no light the seeds germinated but in an abnormal way compared
to the control. The result of this experiment shows that abiotic conditions
have an impact on seed germination.
With light
32 °C
With light
10 °C
Control
With light
23 °C
No light
23 °C
Figure 2 : Effects of light and temperature on seed germination of
Arabidopsis thaliana (all pictures have been taken at 48hours).
Conclusions
 Impact of biotic factors such as bacteria on seed germination
Bacteria have an influence on the germination rate of Arabidopsis thaliana.
Following the germination for more than 24 hours, a visible difference
between the control and the seeds with bacteria present is shown. Seeds
that are closer to the bacteria are more affected than seeds that are far
from the source, suggesting that bacteria can release something that has
an impact in germination
 Impacts of abiotic factors such as light & temperature on seed
germination
After exposing tested seeds under different abiotic conditions it reveals
that the germination is clearly affected by temperature. Even if there is a
lack of light, germination still takes place but in a different manner.
The question now is to find how seeds can sense these abnormal
conditions around them so that they slow their germination down.
Aknowledgments
I really want to thank each and everyone involved in my project. It was a
really interesting week and definitely a great experience. I feel honored
that I had this great opportunity. My future plans are a lot clearer now
and it made me even more excited to study at university soon. A special
thanks goes to my supervisior Hicham Chahtane and the Luiz LopezMolina Laboratory which have opened me the doors to the world of
science, teached me a lot and helped me with my project. Last but not
least I really want to thank the foundation “Schweizer Jugend forscht” that
made this project possible for me, it was a really great-organized week.
I’m glad that I could be part of it.