Name:
Date
Period
Seeds and Toxicity Lab
Purpose: In this investigation we will germinate radish seeds (a living organism) to observe how increasing salt
concentrations or increasing acidity levels can effect seed germination.
Background Information: Radish seeds are sensitive to environmental changes. Seeds are covered by a seed coat
that protects the plant embryo inside from abrasion in rough soil. Radish seeds start the germination process by
taking up water. They are sensitive to the amount of water, water temperature, salt concentrations, and acid
conditions in the water. Water is required for the chemical reactions that begin growth. The seedlings live off food
stored in the seed and begin to grow as soon as hydration takes place.
Water flows from where there is lots of it to where there is less of it. This is called diffusion. Diffusion of water
across the seed coat is called osmosis. When salt concentration increases, water becomes increasingly difficult for
the plant to absorb (or if the water is too salty it will not flow into the seed at all). The amount of salt in water is
called salinity. A plant can actually die in moist soil if the salt concentration becomes high enough.
Increased acidity can also interfere with seed germination. The measurement of the amount of acid or base is called
pH. The pH range is 1 to 14: pH7 is neutral; below 7 acidic; above 7 basic or alkaline. Most seeds prefer a pH
around neutral for germination.
Toxicity tests allow toxicologists to learn about responses of living organisms to doses of chemicals. Dose is the
amount of exposure to a chemical. Response is the reaction to that dose. For example, drinking one glass of milk
may be fine, but drinking a gallon of milk will produce a very undesirable response! In general, increased dose
produces more effects.
In this investigation, you and your teammates are toxicologists. Your project manager has assigned you to construct
a dose-response curve for the effect of a chemical on the germination of seeds. You will determine the effects of a
salt solution or an acid solution on the rate of seed germination.
Why Investigate Salt Concentrations?
Estuaries are places where freshwater meets the sea, and they are rich ecosystems supporting many of the world’s
fisheries. Rivers carry freshwater into the ocean. As rivers are blocked from flowing into the sea, the salinity of an
estuary increases. The creatures living in the estuaries, adapted to a certain salt level, may suffer from the change.
Many dams, even those far from the ocean, also have a significant impact on the marine environment. Blocking a
river’s flow into the ocean can change the shape of a coastline, block fish migrations, and alter marine food webs.
Thus it’s important to keep an eye on what goes on inland. All ecosystems are interconnected; the effect of dams on
estuaries and the ocean is one example.
Why Investigate Changes to pH Levels?
Levels of carbon dioxide in the atmosphere have increased nearly 40 percent since the Industrial Revolution due to
humankind's industrial and agricultural activities and this number continues to increase every day. But, what does
this mean to the ocean and why should we care? Higher levels of dissolved CO 2 lower the ocean’s pH, making it
more acidic. Ocean acidification may negatively affect many ecosystems but causes the most harm to marine
organisms relying on calcium carbonate for their shells and skeletons; at low enough pH levels, the shells will
literally dissolve. Ocean acidification is an emerging global problem with effects that could cascade down the food
chain, with significant impacts on many biological systems. For example, studies have shown that oysters in the
Pacific Northwest are dissolving and that larval development is being hindered in species that are also commercially
important.
What are estuaries? Why are they important to an environment?
How have humans increased the levels of CO2 in the atmosphere?
Seed Toxicity Lab - Procedure
Be sure your procedure includes:
 Logical steps to do the experiment
 Two controlled (kept the same) variables
 One manipulated (independent) variable


One responding (dependent) variable
How often measurements should be taken
and recorded
Question: How does increasing the Salinity or pH (select one) of water affect seed germination?
Procedure:
1. Put on Safety glasses
2. Use the permanent maker to label six empty cups with information from the provided table.
INCLUDE: Period, Group, and Concentration
3. Use the 50mL and the 10mL graduated cylinders to measure the correct amount of water. Pour the
water into each of the labeled cups according to the above table. Use the pipet for small corrections.
4. Use the 50mL and 10mL graduated cylinders to measure the correct amount of chemical. Pour the
chemical into each of the labeled cups of water according to the above table. Use a second pipet for
small corrections.
5. When finished, check that all the cups contain 20mL of chemical solution.
6. Label all six bags with your period, group number, and concentration of chemical.
7. Fill each bag with 1 folded paper napkin.
8. Pour the chemical solutions into the appropriately marked bags.
9. Place 10 seeds equally spaced on TOP of the napkin in the 0% Bag. Remove all the air and seal the
bag – repeat for remaining bags
10. Place the seed bags in a stack, lying flat with the seeds up, in your group container. Record your
observations as instructed by your teacher.
11. The next class period record the amount of seeds that have sprouted and record that in the data table.
Record any qualitative data
12. Repeat Step 11 on Day 3.
Two Controlled Variables:
One Manipulated Variable :
One Responding Variable:
Seeds and Toxicity Lab Data
Qualitative Observations – describe at least two per day:
1.
2.
3.
4.
5.
6.
Quantitative Observations: (Table and Graph)
TITLE: Seed Death vs. Chemical Concentration Table
Dose
Response
(% Concentration
Day ____
Day ____
of Chemical)
# sprouted
# not sprouted
# sprouted
# not sprouted
(alive)
(killed)
(alive)
(killed)
0%
6.25%
12.5%
25%
50%
100%
TITLE: Seed Death vs. Chemical Concentration Graph
Seeds and Toxicity Lab Conclusion
In your conclusion, be sure to:
 Answer the experimental question.
 Include supporting data from the Seed Death vs. Chemical Concentration table.
 Explain how these data support your conclusion.
 Provide a scientific explanation for the trend in the data.
Question: What is the effect of different the chemical concentrations on seed death? (Refer to your test chemical
acid solution or salt solution.)
Conclusion:
Seeds and Toxicity Lab Application
1. In this lab, how did increasing salinity affect seed death?
2. In this lab, how did increasing acidity affect seed death?
3. Estuaries are nursery grounds for marine organisms. Why is this important for biodiversity and commercial
fisheries?
4. What negative impact might increasing salt levels have on an estuary ecosystem?
5. How do increasing levels of CO2 affect the world’s bodies of water?
6. What negative impact might increasing CO2 levels have on organisms in the Puget Sound ecosystem?
7. What steps would you need to consider if you were setting legal policy to protect these ecosystems?
(continue on back if needed)