MediumBiologyHigh School (9–10)GeneralPlant Biology › Plant Hormones and MovementsHuman Body › Hormones and the Endocrine SystemConceptual
Farah lays a young bean seedling flat on wet cotton inside a dark box, so that its root and shoot…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Farah lays a young bean seedling flat on wet cotton inside a dark box, so that its root and shoot point sideways. After two days she opens the box. Describe what the root and the shoot have done, and name each response.
Need a reminder? The key ideaShow
A tropism is a growth movement towards (positive) or away from (negative) a stimulus. Shoots grow towards light and away from gravity. Roots grow towards gravity and towards water. A pollen tube grows towards a chemical made by the ovule. A part bends when one side grows faster than the other.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The stimulus. The box is dark, so the only direction-giving stimulus is gravity.
Step 2. The root. It curves down, towards gravity. This is positive geotropism.
Step 3. The shoot. It curves up, away from gravity. This is negative geotropism.
Answer: the root bends down and the shoot bends up, both by growth: positive geotropism of the root and negative geotropism of the shoot.
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