A Wonderleaf question
How do roots know which way is down?
a real page from the book
Roots grow downward because cells in the root tip can feel gravity. Tiny heavy grains settle toward the lower side, and that position changes plant signals. The root then grows unevenly, curving until its tip points into the soil.
The same kind of gravity sensing helps shoots choose the other direction. In roots, the growth pattern bends them down toward water and anchoring ground; in shoots, it helps stems lift toward light, so one seed can sort out two opposite paths.
Wonder words
- gravity
- statoliths
- auxin
- shoots
Try it out
Lay a sprouted bean on damp paper, turn it sideways, and check which way the root curves over the next few days.
Read the whole picture book
Watercolour scenes, straight answers, about three minutes cover to cover.
Open the picture bookKeep wondering
- How do plants drink water?
- Why do fruits taste sweeter when they are ripe?
- How do plants make the food we eat?
- Why do apples turn brown after cutting?
- Why do bananas turn brown?
One more wonder: Why is space so dark?
And the next question?
Ask anything — Wonderleaf writes and illustrates a picture book for it. That's the whole idea.
Ask your own questionThe next wonder, by email
A new question goes up every Sunday evening. We email it to you Monday morning, free to read that week.
One wonder a week, nothing else, ever. Unsubscribe in one click.