What Effect Does the Position of Artificial Light Have on Plant Growth?
Project Idea by: David Murphy
Light is necessary for healthy plant growth. The process by which plants use light energy, water, and carbon dioxide to make food is called photosynthesis. Photosynthesis occurs in plants that have chlorophyll, which is a green chemical that can capture light energy.
Plants must have all the light colors in the visible spectrum to grow properly. Some of the light colors promote stem growth, flowering, leaf formation, and dark green foliage. The blue and red parts of the visible spectrum are most important for photosynthesis.
Artificial light is light from a man-made source. Indoor plants that don't get enough sunlight can survive well with white artificial light. Indoor lighting can be placed in different positions in relation to the plants. For example, for a dramatic display, lighting might be placed above and/or beneath plants. A project question might be, "What effect does the position of artificial light have on plant growth?"
Clues for Your Investigation
Design a method for exposing plants to artificial light from different directions: overhead, beneath, and to the side. For example, plants can be placed in separate boxes so that the only light received is from an opening in the box. The testing should be in an unlit room or one as dark as possible so that most or all of the light comes from the testing lamps. All plants should be exposed to light for the same amount of time. Design a method for measuring plant growth. You may wish to start with seeds. After sprouts appear above the soil, begin measuring plant growth by measuring the length of the stems. Since sunlight basically comes from above plants, the light from above the plants can arbitrarily be selected as the control.
Independent Variable: Direction of light
Dependent Variable: Plant growth—length of stems
Controlled Variables: Testing method; measuring method; type of plants, potting soil, containers, and environmental conditions; types and wattage of light bulbs; amount of light exposure; distance of light from the plants
Control: Arbitrarily selected light from above
Other Questions to Explore
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