Introduction: You have learned how the Sun
affects the growth of plants. This experiment will demonstrate how
plants react to the presence of light and how the plant hormone
auxin works in plants.
Vocabulary: auxin, tropism, phototropism,
- Shoebox with a lid or cardboard box with
- Paper cup
- 3 bean seeds
- Cardboard cut to width of
- Potting soil
- Tape or glue
- Fill the paper cup with potting
- Plant the beans in the soil. Plant about
- Water the soil and allow the beans to
- Stand the shoebox on its narrow
- Cut two cardboard pieces that fit inside the
shoebox, these will be the maze walls so put alternating holes in
them big enough for the plant to get through (approx.
- If using a cardboard box cut alternating
holes in the divider. Holes should be about 2 inches
- Make sure the walls will stay in place with
tape or glue.
- Cut a hole in the top that is big enough for
the plant to get through.
- As soon as the plant sprouts put it inside
the shoebox at the opposite end from the hold you have
- Put the lid on the shoebox and make sure it
will remain in place.
- Place the box near a sunny
- Open the lid daily to make note of plant
- Water the soil when needed.
- Continue to observe until the plant grows
out the hole in the lid.
- Do you think the plants will wind their way
through the holes to the outside of the box?
- What does this experiment tell us about how
plants respond to light from the Sun?
- Are the plants sensitive to
- How can you tell they are sensitive to
- Which way do the stems always
- Which way do the roots always
- Do you think that turning the seed upside
down would affect the way the plant grows?
- List three things that are necessary for
The plant winds around all obstacles and out
the hole in the lid just to get to the light. The plant is growing
toward the light because of phototropism. A buildup of a plant
growth chemical called auxin happens on the dark side of plant
stems. Auxin causes cells to grow longer on the other side of the
stem which forces the stem to bend toward the light.
If the seed were planted upside down, the
roots would start growing from the top of the seed and the stem
would come out from the bottom. Then the would both turn around and
grow the correct way. The roots would grow down because of gravity
(geotropism) and the stem will always grow toward the Sun
(phototropism). Phototropism is the result of the presence
Plants need gravity, light, and water for
survival. Plants will also grown toward favorable conditions and
away from unfavorable conditions.
The light energy from the Sun causes the
plants to produce food in their leaves by photosynthesis. This
enables them to grow.
©Copyright 1998 Elizabeth
Beckett, Holly Bernitt, and Vishwa Chandra.