Mrs. Keadle JH Science
Forces in Living Things Lab
Lab 1: Emergence of Seedlings
In this lab, each class is going to grow a seedling to watch the effects of
forces on a young, growing plant.
The Sleeping Seed
When seeds are planted, it may take several days before we can see anything
going on. Well, actually, lots of things are happening that you just can’t see right
away. Right now, the seeds are dormant (almost like sleeping) but the moisture
will trigger them to start their growth cycle. This process is called germinating.
Once the water soaks into the seeds, it sends a signal to tell the seed it can start
to grow.
The part of the seed that you see right now is called the seed coat. It protects the
young plant. Inside of the seed coat is the real growing part of the baby seed.
It Starts…
Watch the seeds for changes. In a day or two the seed coats will start to split, and
you’ll see the root tip sticking out. Scientists call that part the radicle. Watch it
dive into the crystal clay to become the main root. Eventually, it will branch out to
become the root system. In order to sprout, the tiny seedling has to overcome
forces. The stem and first leaves have to overcome gravity and the weight of the
soil on top of them to emerge from the ground. The roots have to be strong
enough to push through the soil beneath them.
First Leaf…
The radical drinks up water so that the plant can start to grow. As the stem grows
and the seed coat splits off, you will see the first new green leaf. The first leaf is
called a cotyledon. The tiny plant needs water, carbon dioxide, and sunlight. The
leaves absorb carbon dioxide through tiny opening on the underside of the leaf
called stomata. Sunlight can pass through the leaf and is collected in the
chlorophyll of the green parts of the plant. Water is absorbed through the roots
and in some cases the leaves.
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Forces in Living Things Lab
Mrs. Keadle JH Science
Materials:
clear tube or cup
crystal clay
pinto beans
spring water
Procedure:
1. Place half a scoop of crystal clay in the cup.
2. Add a small amount of spring water.
3. The crystals will expand as they absorb water. Add water as needed until there
is enough to plant a seed in.
4. Wait 20 to 60 minutes. If any of the crystals are still exposed above the water
line, add more water one teaspoon at a time. Re-Check every 30 minutes and
add water as needed until the crystals have stopped expanding. If the crystals
reach the top of the tube, remove some until it is no more than ¾ full. If there
is too much water, pour some off of the top.
5. Add the beans. Do not bury them and make sure that the water level is high
enough to keep the seeds moist, but not soaked, during the first 3 days.
6. Put the seed in a bright, cool place.
7. Add water as needed to keep the water level just below the top of the crystals.
8. After 1-2 days, take out any seeds that have not germinated.
Hypothesis: Finish this sentence on your scientific method flow chart to describe
what you think will happen to the beans:
I think the roots will___________________,
and the stems and leaves will _____________________________ .
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Forces in Living Things Lab
Mrs. Keadle JH Science
Lab 2: Geotropism
In this lab, we will observe how gravity can affect seedling growth.
Have you ever wondered how a plant knows which way to grow? Imagine how
Earth would look if plants could grow in many different directions. On Earth, a
force called gravity signals young seedlings to push their stems up and their roots
down.
Materials:
4 bean seeds
petri dish
tape
cotton balls
tap water
Procedure:
1. Take four soaked seeds, and place them in the bottom of a petri dish with
the seed “dimples” facing toward the center. A seed should be placed on the
12, 3, 6 and 9 o’clock positions of the petri dish.
2. Place cotton balls on top of the seeds to hold them in place.
3. Using the spray bottle, dampen the cotton balls. Do not get them so wet
that they drip.
4. Carefully cover the seeds with the petri dish lid.
5. Close the petri dish and tape the lid in place.
6. Diagram the petri dish set-up at the beginning of the lab and after the seeds
sprout.
7. Write the group member names on a small piece of paper and tape it to the
back of the petri dish.
8. Place the petri dished vertically in a dark place such as a closet or cabinet.
Hypothesis: How do you think each of the bean seedlings will grow? Write a brief
hypothesis on your scientific method chart. Then draw a detailed diagram of your
hypothesis on your lab sheet.
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Forces in Living Things Lab
Mrs. Keadle JH Science
Lab 3: Turgor Pressure
In this lab, we will observe how water can affect the rigidity of a plant.
We know that plants require sunlight, water and soil to survive. Water is used by
the plant for many different purposes. First, water is needed for photosynthesis.
Plants also need water to “inflate” their cells and keep the stems and leaves
upright. When a plant does not have enough water, it will wilt and droop. If it
goes long enough without water the plant cells die.
The water inside the cell puts pressure on the cell just like water inside a balloon
pushes out on the balloon. The pressure that the water exerts is called turgor
pressure. High turgor pressure in a plant keeps all of the leaves and stems upright.
Low turgor pressure causes the plant to wilt.
If a plant is placed in salt water, the water inside the cell is pulled out and
dehydrates the cell. When placed in fresh water, water can enter the cell.
Materials:
strips of potato
salt
water
2 beakers
Procedure:
1. Soak some strips of potato in salt water and some in fresh water overnight in a
refrigerator.
2. Take one potato strip that was soaked in salt water and that was soaked in
fresh water.
3. Bend each strip until it breaks.
Hypothesis: Which potato strip will have high turgor pressure and which one will
have low turgor pressure? Write your hypothesis on your scientific method flow
chart.
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Forces in Living Things Lab