What is gravitropism?

Gravitropism is the ability of plants to sense gravity. Roots grow downward (positive gravitropism) to find water, while stems grow upward (negative gravitropism) toward sunlight. This ensures plants always orient correctly, even in the dark.

Can plants grow upside down?

Yes! Hanging planters grow plants upside down. The roots still follow gravity downward, while the stem bends to grow upward toward light. Plants use both gravity and light signals to navigate direction.

How do roots feel gravity?

Special cells in the root tip called statocytes contain tiny, dense starch granules called statoliths. Gravity pulls these granules to the bottom of the cell, triggering the root to grow in that downward direction.

What happens if you rotate a plant on its side?

Within hours, the roots bend and start growing downward again while the stem bends upward. This involves moving plant hormones called auxins to redirect growth toward or away from gravity.

Quizzy

Living Things

The Gravity Maze: How Roots Know Which Way is Down

April 8, 2026Ages 3–9

Q-bo's Answer

Plants have tiny 'weight' sensors in their roots. Even if you turn a plant sideways, the roots will quickly turn and head back down toward the center of the Earth!

📖 Explanation

🎒 For Ages 6-9

Statocytes and Gravity

Inside the tips of roots are special cells called 'statocytes' containing heavy starch grains. These grains sink to the bottom of the cell due to gravity, telling the plant exactly which way is 'down.' This allows plants to find water and nutrients in the soil effectively.

❓ Frequently Asked Questions

What is gravitropism?: Gravitropism is the ability of plants to sense gravity. Roots grow downward (positive gravitropism) to find water, while stems grow upward (negative gravitropism) toward sunlight. This ensures plants always orient correctly, even in the dark.
Can plants grow upside down?: Yes! Hanging planters grow plants upside down. The roots still follow gravity downward, while the stem bends to grow upward toward light. Plants use both gravity and light signals to navigate direction.
How do roots feel gravity?: Special cells in the root tip called statocytes contain tiny, dense starch granules called statoliths. Gravity pulls these granules to the bottom of the cell, triggering the root to grow in that downward direction.
What happens if you rotate a plant on its side?: Within hours, the roots bend and start growing downward again while the stem bends upward. This involves moving plant hormones called auxins to redirect growth toward or away from gravity.

Step 1 / 2

🧪 The Sideways Seed Challenge

~168h

Grow seeds in a clear container and flip them to watch the roots correct their path.

🛒 Supplies

📋 Steps

1
🫘 Plant in clear gel
Grow a bean seed in a clear jar with wet paper towels so you can see the roots.
2
🔄 Flip the jar
Once the root is 2cm long, turn the jar sideways and watch what happens over 24 hours.

Watch the Video

Time-lapse footage shows roots making a U-turn when the plant is moved, making the invisible force of gravitropism obvious.

The Gravity Maze: How Roots Know Which Way is Down