Background: Plant roots always grow downward because specialized cells in root caps detect and respond to gravity. This is an example of a tropism. A tropism is a turning toward or away from a stimulus in the environment. Growing toward gravity is called geotropism . Plants also exhibit phototropism , or growing toward a light source. This response is controlled by a plant growth hormone called auxin . As shown in Figure below , auxin stimulates cells on the dark side of a plant to grow longer. This causes the plant to bend toward the light.

Situation: Sue loved having  pretty plants in her apartment but often forgot to take care of them. One day she was sitting in the kitchen and noticed her aloe was was growing  with all the branches curving towards the window. When she picked it up to turn it she notices some of the roots were growing out of the bottom of the pot. She sighed and made a mental note to stop at the garden center for a deeper pot tomorrow.

Question: Were the branches growing towards or away from stimuli?

Situation: Sue loved having  pretty plants in her apartment but often forgot to take care of them. One day she was sitting in the kitchen and noticed her aloe was was growing  with all the branches curving towards the window. When she picked it up to turn it she notices some of the roots were growing out of the bottom of the pot. She sighed and made a mental note to stop at the garden center for a deeper pot tomorrow.

Question: Where the branches growing towards or away from the sunlight?

Situation: Sue loved having  pretty plants in her apartment but often forgot to take care of them. One day she was sitting in the kitchen and noticed her aloe was was growing  with all the branches curving towards the window. When she picked it up to turn it she notices some of the roots were growing out of the bottom of the pot. She sighed and made a mental note to stop at the garden center for a deeper pot tomorrow.

Question: Were the roots growing up or down?

Situation: Sue loved having  pretty plants in her apartment but often forgot to take care of them. One day she was sitting in the kitchen and noticed her aloe was was growing  with all the branches curving towards the window. When she picked it up to turn it she notices some of the roots were growing out of the bottom of the pot. She sighed and made a mental note to stop at the garden center for a deeper pot tomorrow.

Question: Where the branches longer on the side closest or farthest from the light?

Situation: Beth was getting her vegetable garden ready for the season. She had several small plants ready to transplant into her garden. First Beth dug several holes to put the plant's in. She made sure the soil at the bottom of each hole was loose then settle the root balls into the wholes and covered them. She was also careful to select a spot where the plants would get sunlight from several different directions throughout the day.

Question: Will the plant roots grow up or down?

Situation: Beth was getting her vegetable garden ready for the season. She had tried one of those upside down planters last year but it didn't go so well. The tomato plant grew down at first but then started curving upwards like a U shape. This year she was going back to a traditional garden. She had several small plants ready to transplant into her garden. First Beth dug several holes to put the plant's in. She made sure the soil at the bottom of each hole was loose then settle the root balls into the wholes and covered them. She was also careful to select a spot where the plants would get sunlight from several different directions throughout the day.

Question: What was the upside down tomato plant growing towards?