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2. Plants need Light


1. Mix about 5 gallons of Grow nutrient water.

2. The overhead light is on for a 12-hour period each day.

3. The hydroponic is planted with small pots (25) with sunflower seeds. The sunflower seeds are allowed to sprout and reach a height of from one to two inches in length.

While the sunflower seeds are starting, the students can discuss light. Any stories about house plants or plants in the garden can be mentioned. A topic is what does a plant like in light.

An activity is supplied on sunlight. The activity is coloring a poster that shows light and a plant. The activity is to provide students with skills on the necessity of light for plant growth.

4. Once the sunflowers are about 2 inches tall, the students are encouraged to invent some type of cover to test the effect of light on the plants.

Construction paper, scissors, tape, paper punch, and papers that do not let light through.

5. Students work in teams and have two plants they can use for designing a light shielding

6. At the beginning of each day, the students take off their shields and collars for the plants and make note of changes. They also measure the plants. They should also draw the plants.

    Data for the experiment
  • draw a picture of the plant
  • measure the plant
  • draw a close up of anything special or unusual about the plant<

The experiment should continue at least a week.

Expected results.

A few collars should have covering except for one small hole in a side. In these cases, the plant will push itself towards the light. It may even grow sideways if the hole is low enough. Filters of colors should show plants that are very pale or with strange pigments.

The light experiment brings up several questions of interest.

Why does the plant bend, or how does it bend.

How does the plant know where the sun is?

How does it bend towards the sun?

Picture of phototropism.

Photo of the cells elongating on the shaded side

Qualities of Light


1. Students discuss how to experiment with quality of light.

What do we mean by light quality?

What we see as visible light is the light between violet and blue, or the colors of a rainbow.

When all these colors are mixed together, we see white light (or colorless light).

When all the colors are missing we see dark or black.

Why does the plant change with different colored lights?

The sunflowers in the An activity is supplied on water. This activity compares hydroponic water use with soil based plant water use.


1. This activity is exactly as in the Qualities experiment above, except now the students use colored transparent films of a variety of colors and shapes. They cover the sunflowers in the grower and then record the results every day for a week.

Coloring a poster that shows light and a plant. The activity is to provide students with skills on the necessity of light for plant growth.

Plants require different qualities of light.

Revised: 1 May 2016
Copyright © 2016 Institute for Simplified Hydroponics