Gravitropism in Seedling Stalks

In this demonstration, seedling stalks (hypocotyls) are placed horizontally in dark containers, and within about an hour they begin to bend upward, showing negative gravitropism. This illustrates how plants sense gravity and redirect growth through hormonal signaling.

1. Cut a fresh seedling stalk (hypocotyl).
2. Attach the stalk to the inside of a film canister lid.
3. Place the lid back onto the canister so the stalk lies horizontally.
4. Leave the setup undisturbed for about an hour.
5. Open the container and observe that the stalk has bent upward, demonstrating negative gravitropism.

Geotropism - Plants Defying Gravity - Primrose Kitten Academy:

📄 Demonstrating Gravitropism in Seedling Stalks - Science & Plants for Schools: https://www.saps.org.uk/teaching-resources/resources/184/student-sheet-7-demonstrating-gravitropism-in-seedling-stalks/

• Try using seedlings of different ages to see if the rate of bending changes.
• Place the canisters at different angles (not just horizontal) to observe varying responses.

• Use a clean, sharp blade or scissors when cutting seedlings.
• Handle blades with care and cut away from your body.
• Dispose of plant material properly after the experiment.

• What is negative gravitropism? (It is the upward growth of shoots away from gravity.)
• Why do roots grow downward while shoots grow upward? (Roots show positive gravitropism to anchor and seek water; shoots show negative gravitropism to reach light for photosynthesis.)
• How do plants sense gravity? (Through statoliths settling in endodermal cells, triggering hormone redistribution.)
• Which hormone plays a major role in this response? (Auxin, which redistributes and promotes bending.