Phototropism
Shoots bend towards light, roots bend away.
A seedling by the window
A seedling grows in a pot. Light comes from the left side. After a few days, the shoot and the root have grown in particular directions.
What do you think happens to the shoot and to the root?
What this lesson covers
The idea
In phototropism, shoots respond to light by bending towards it, while roots respond by bending away from it.
A seedling by the window
A seedling grows in a pot. Light comes from the left side. After a few days, the shoot and the root have grown in particular directions.
What do you think happens to the shoot and to the root?
- The shoot bends towards the light and the root bends away from it
- Both the shoot and the root bend towards the light
- Neither the shoot nor the root changes direction
Light from one side
Press Next step. Light comes from the left.
Two opposite bends
The same light makes the shoot and the root bend in opposite ways. That is why the book speaks of two different kinds of phototropic movement.
In phototropism, shoots respond to light by bending towards it, while roots respond by bending away from it.
Notes
In phototropism, shoots respond to light by bending towards it, while roots respond by bending away from it.
Check yourself
In phototropism, how does a shoot respond to light?
In phototropism, how does a root respond to light?
Light falls on a seedling from the right. Which is correct?
Which trigger causes phototropism?
- It bends away from the light. Roots, not shoots, bend away from light.
- It bends towards the light — correct. Yes!
- It does not change its direction. Shoots respond to light by bending towards it.
- It bends towards the light. Shoots bend towards light. Roots bend away from it.
- It folds up and droops. Folding and drooping is the quick movement of the sensitive plant, which does not involve growth.
- It bends away from the light — correct. Yes!
- The shoot bends to the right and the root bends to the left — correct. Yes!
- The shoot bends to the left and the root bends to the right. That is the opposite. The shoot bends towards the light, which is on the right.
- Both bend to the right. The root bends away from the light, so it bends to the left.
- Gravity. Gravity causes geotropism, the upward and downward growth of shoots and roots.
- Light — correct. Yes!
- Touch. Touch makes a tendril circle around a support.