Phototropism & Gravitropism Lab Community
Questions, answers and tips from people who use the Phototropism & Gravitropism Lab. Rotate the pot and move the light, predict which way the shoot and root will grow, then run the simulation and check your prediction..
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This page shows only real posts from real people, so it starts empty. The guide below has the questions people most often have about the Phototropism & Gravitropism Lab. Pick one to start a thread, or write your own.
From the tool guide: common questions about Phototropism & Gravitropism Lab
The items below are not posts by community members. They come from the written guide for this tool and are here to get a conversation started. Use “Ask a follow-up” to open a thread about any of them.
Why do shoots grow up and roots grow down?
Shoots combine negative gravitropism with phototropism to reach for light, while roots use strong positive gravitropism to anchor and find water and nutrients in the soil.
From the tool guide Ask a follow-upWhat happens if you rotate a growing seedling on its side?
Statoliths resettle to the new lowest side of the cells, and within hours the shoot curves back upward and the root curves back downward.
From the tool guide Ask a follow-upKey ideas
- Shoots show negative gravitropism (grow away from gravity) combined with positive phototropism (grow toward light).
- Roots show strong positive gravitropism and are largely insensitive to light.
- Dense statoliths inside root and shoot cells settle toward the lowest side under gravity, triggering the auxin redistribution that curves the organ.
- Rotating a plant makes the statoliths resettle, so the plant actively re-aims its growth at the new 'down'.
Things to try
- Set the light straight up and predict the shoot direction before running.
- Rotate the pot 90 degrees and predict again - did your answer change?
- Move the light to a hard side angle and see how far off gravity alone the shoot ends up.
- Try to predict correctly three times in a row.
Where this is used
Farmers count on gravitropism when planting seeds any-side-up, and space agencies studied plant tropisms on the International Space Station to see how growth changes with weaker or absent gravity.
How to ask a question people can answer
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