The Effects of pH and
Temperature on the Germination
of Raphanus sativus Seeds
Keara Miley – Lake Shore
Robin Smith – Lake Shore
Terminology
• Two-Factor Design of Experiment
– (DOE)
• Raphanus sativus
– (Radish)
• Germination
– When a seed starts to sprout
• pH
– How alkaline or acidic a substance is
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How does pH affect germination?
• pH affects germination because the acid
breaks down the seed coat and allows
more water to get absorbed
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Temperature affecting Germination
• If temperature is too high, moisture
evaporates from the soil
• If temperature is too low, water absorption
slows
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Why Do The Experiment?
• More areas we can grow food, the more
food we can grow
• The purpose of the experiment was to find
the pH level and temperature that would
cause the most Raphanus sativus (radish)
seeds to germinate
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Problem
• How do different levels of pH and
temperature affect the germination of
radish seeds?
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Hypothesis
• If the surrounding temperature is 35ºC
and the pH level of the water sprayed on
the seeds is 4.0, then the most radish
seeds will germinate
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Values
pH
-
4.0
Standard
6.0
Temperature (°C)
+
-
8.0
28
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Standard
30
+
35
8
Materials
•
•
•
•
•
•
•
•
•
Source of tap water
Analytical balance
100 mL spray bottles
Paper towels
Ziploc bags
Incubator (35°C)
Refrigerator
pH test strips
tweezers
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Procedure
• We mixed the water with either baking
soda or citric acid to change the pH and
get a high, a low, and a standard
concentration
• We sprayed the concentrations onto the
radish seeds placed in Ziploc bags
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Procedure
• We then placed the bags into areas with
the different temperature levels
• After 3 days, we recorded the number of
seeds that germinated in a table
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Procedure
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Number of Seeds Germinated
Data Analysis
10
8
8.17
8
6
4
2
0
-1
1
pH
• The effect of pH on the
germination of radish
seeds was -0.17 units
• On average, as pH
increased, the number
of seeds germinated
decreased by 0.17 units
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Number of Seeds Germinated
Data Analysis
10
8.33
8
7.83
6
4
2
0
-1
1
Temperature (°C)
• The effect of
temperature on the
germination of radish
seeds was 0.5 units
• On average, as
temperature increased,
the number of seeds
germinated increased by
0.5 units
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Data Analysis
Number of Seeds Germinated
10
8.33
8
8.33
8
7.67
6
4
2
0
-1
1
Temperature C
• There may be an
interaction between the
two line segments
because they are not
parallel
• The effect of the graph
is 0.16 units
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Observations
Date
Observation
March 29 Bags and seeds are set up
April 1
April 2
April 5
All standards have germinated and quite a few
of the ones in the incubator. No germination in
the refrigerator
More have germinated in the incubator. Still
no germination in the refrigerator
Still no germination in the refrigerator. We will
retry this part in warmer area of 28°C
April 11 Seeds germinated in the warmer temperature
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Hypothesis
• Hypothesis was accepted
• Most seeds germinated in 35°C
temperature and pH level of 4.0
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Recap
• Set out to find what pH level and
temperature germinated the most seeds
• We hypothesized that most seeds would
germinate at 35ºC and a pH of 4.0
• Conducted experiment
• Sprayed different pH levels on radish
seeds
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Recap
• Set the seeds in areas of different
temperatures
• Recorded how many seeds germinated
after three days
• Found a temperature of 35°C and pH of
4.0 germinated the most
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Design Flaws and Errors
• Testing in an area of 22°C was too cold
– Retested in an area of 28°C
• Initially added too much citric acid and
baking soda
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Further Study
•
•
•
•
Different levels of pH
Wider ranges of temperatures
Different types of plants
Different soil types
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Real Life Application
• Retailers find best source to buy stock
– Profits increase
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