Root for It

Root for It
Close this window to go
back to the activity page.

Were you surprised by how long the roots became? Different kinds of plants have different kinds of roots. The root of a carrot plant is long and straight but the roots of a corn plant grow out to the sides. You can put rocks or other obstacles in the way of the roots of your plants and the roots will find a way around them. Have you ever seen a carrot that had a funny shape? That root had to find its way around an obstacle and you got a weird vegetable.

Tropisms
The Back Story mentions an experiment to look at geotropism. After your plants have grown 1 to 2 inches tall, turn the root chamber so that it is on its side. The roots of a plant will grow towards the Earth and the stem will grow away from the Earth. If you have a record player at your house, you can put the root chamber on the turntable and let it spin for several days. What will happen to the roots and stems in this artificial gravity?

Phototropism - (photo is Greek for light) - Most stems will bend toward the light. It is believed that stems bend because a hormone in the stem makes cells on the darker side grow faster than those on the lighter side. Can you design an experiment that will test whether your bean seeds grow toward the light?

Negative Phototropism - When a root grows toward gravity, that is called positive geotropism. When the stem grows away from gravity, that is called negative geotropism. Most plants exhibit positive phototropism because they grow toward the light. There are some plants that actually grow toward a shadow. Plants that climb (such as ivy) grow toward a shadow that might be made by a wall or tree.

Hydrotropism - (hydro is Greek for water) - Plant roots grow toward moisture. Can you think of a way to use your root chamber to check for hydrotropism?

Thigmotropism - (thigmo is Greek for touch) - Some plants react to touch. You might want to visit a greenhouse to see a sensitive plant. When a sensitive plant's leaves are touched, they fold up and droop.