Best examples of investigating plant growth rate under light for science fairs

Real examples of investigating plant growth rate under light

Let’s skip the theory and jump straight into real examples of investigating plant growth rate under light that students actually can run. All of these can be scaled up or down depending on your grade level, time, and budget.

Example of sunlight vs. LED vs. fluorescent light

One of the best examples of examples of investigating plant growth rate under light compares common light sources students see every day.

You might grow fast‑germinating plants such as radishes, lettuce, or beans in three groups:

• Group A: Near a sunny window (indirect natural sunlight)
• Group B: Under a white LED grow light
• Group C: Under a cool white fluorescent shop light

All groups get the same soil type, pot size, watering schedule, and temperature. The only variable is the light source.

Students measure:

• Plant height every two or three days
• Number of leaves per plant
• General appearance (color, stretching, leaf size)

After three to four weeks, you can compare growth rate under different lights. A lot of modern research shows that LED lighting is highly efficient for plant growth because it can be tuned to wavelengths plants use best. The U.S. Department of Energy has a helpful overview of LED plant lighting and energy use here: https://www.energy.gov/eere/ssl/lighting-market-characterization.

This kind of setup gives one of the clearest examples of how different light sources affect growth rate, and it mirrors the way commercial greenhouses are switching from older lamps to LEDs.

Example of red vs. blue vs. full‑spectrum light

If you want a project that sounds scientific but is still doable at home, color experiments are some of the best examples of investigating plant growth rate under light.

Plants mainly use red and blue wavelengths for photosynthesis. With affordable LED grow bulbs or RGB LED strips, students can create three light treatments:

• Red‑dominant light
• Blue‑dominant light
• Full‑spectrum white light (control)

You might grow the same number of basil or lettuce plants under each light type. Keep distance from the light and daily light duration the same for all groups.

Students track:

• Daily or twice‑weekly height
• Leaf count
• Average leaf length or width
• Final fresh mass (weighing plants at the end)

NASA and other space‑agriculture programs use this kind of setup to optimize plant growth in controlled environments. NASA’s Space Biology program has public information on light and plant growth here: https://www.nasa.gov/space-biology.

This project gives one of the best examples of how light color influences not only growth rate but also plant shape and leaf development.

Example of light intensity and distance from the lamp

Another powerful example of investigating plant growth rate under light tests how far plants can be placed from a light source before growth slows down.

Using a single LED panel or grow bulb, arrange plant trays at different distances, such as:

• 6 inches from the light
• 12 inches from the light
• 18 inches from the light
• 24 inches from the light

This gives several real examples of how intensity drops with distance. You can use a cheap light meter or even a smartphone app (with calibration) to estimate relative light levels at each distance.

Students measure:

• Growth rate in height per week
• Time to first true leaves
• Time to first flower (if using a fast‑flowering species like some dwarf peas)

The science behind this connects nicely to the inverse square law of light intensity. University extension programs, such as the University of Minnesota Extension, provide accessible explanations of light intensity and plant growth: https://extension.umn.edu/houseplants/light-indoor-plants.

This is one of the best examples of examples of investigating plant growth rate under light because it blends physics and biology in a single experiment.

Example of day length (photoperiod) and growth rate

Plants don’t just care about how bright the light is. They also react strongly to how many hours of light they receive per day—called photoperiod.

To design this, students grow identical plants under the same type and intensity of light but vary day length using timers:

• Short day: 8 hours of light, 16 hours of dark
• Medium day: 12 hours of light, 12 hours of dark
• Long day: 16 hours of light, 8 hours of dark

This gives real examples of how day length affects growth rate, especially in leafy vegetables and some flowering plants.

Students record:

• Weekly height increases
• Leaf number over time
• Whether the plants stay compact or stretch
• If flowering occurs earlier or later in different treatments

Photoperiod research is a major part of modern horticulture and agriculture. For background reading, students can look at university horticulture notes, such as those from Cornell University’s horticulture program: https://cals.cornell.edu/school-integrative-plant-science.

Example of shaded vs. full‑sun conditions

Not every project needs artificial lights. Some of the simplest examples of investigating plant growth rate under light use natural sunlight with different levels of shade.

Students can:

• Grow one set of plants in full sun on a balcony or patio
• Grow another set under a shade cloth or under a tree where light is filtered

The key is to measure actual light levels if possible, using a light meter or a phone app, to turn this into data instead of just a vague description.

Measurements might include:

• Growth rate in height per week
• Leaf area (trace leaves onto paper and measure)
• Stem thickness

Shaded plants often grow taller and thinner (stretching for light), while full‑sun plants stay shorter and sturdier. This example of light‑driven change is easy to photograph and graph for a science fair board.

Example of indoor window direction (north vs. south vs. east vs. west)

Indoor gardeners already know that not all windows are equal. This makes a very relatable example of investigating plant growth rate under light for students who only have access to windowsills.

You can grow sets of identical plants at different window orientations:

• South‑facing window (most light in the Northern Hemisphere)
• East‑facing window (morning light)
• West‑facing window (afternoon light)
• North‑facing window (lowest light)

Students observe and measure:

• Height changes over time
• Leaf color and any yellowing
• Direction of growth (do plants lean toward the glass?)

This project gives real examples of how light exposure across a house or classroom affects plant growth rate, and it helps connect the experiment to everyday life.

Example of combining light and fertilizer for a more advanced project

For advanced middle or high school students, a more complex example of investigating plant growth rate under light looks at how light interacts with another variable, such as fertilizer.

You might design a two‑factor experiment:

• Light: high vs. low intensity
• Fertilizer: standard vs. reduced nutrient solution

That creates four treatment groups. Students can see whether low light and low nutrients together slow growth more than either factor alone.

This mirrors how professional plant scientists test multiple environmental factors at once. The USDA’s Agricultural Research Service publishes research summaries on controlled environment agriculture and lighting strategies: https://www.ars.usda.gov.

These combined‑factor designs are some of the best examples of investigating plant growth rate under light for students who want a project that looks closer to real research.

Designing your own experiment using these examples

All of these real examples of investigating plant growth rate under light share some common design features that make them scientifically strong.

Choosing a plant species

For school projects, quick‑growing species work best. Common choices include:

• Radish
• Lettuce
• Basil
• Beans or peas
• Fast‑growing grasses (like ryegrass)

These plants germinate quickly and show visible differences in growth rate under different light treatments within a few weeks.

Controlling variables

When you adapt any example of a light experiment, keep as many other factors the same as possible:

• Same soil type and amount
• Same pot size and drainage
• Same watering schedule and water amount
• Similar temperature and air flow

This way, when growth rate changes, you can reasonably argue that light conditions were the main cause.

Measuring plant growth rate

To make your project data‑rich, plan ahead for how you will measure growth. Common options include:

• Height: Measure from soil surface to the tallest point of the plant using a ruler.
• Leaf count: Count fully opened leaves at each time point.
• Leaf size: Measure length or width of a chosen leaf.
• Fresh mass: At the end of the experiment, gently wash and blot plants dry, then weigh them.

Recording data at regular intervals (for example, every two or three days) gives you enough points to calculate growth rate and plot graphs.

Connecting your project to real research

Science fair judges love when students connect their experiments to real plant science. The examples of investigating plant growth rate under light in this guide line up with several active research areas:

• Controlled environment agriculture and vertical farming, where growers use LED lighting and specific light recipes to maximize yield per square foot.
• Space biology, where agencies like NASA test how to grow food for long‑duration missions using red and blue LEDs.
• Urban agriculture, where city farms use different light intensities and day lengths to grow greens year‑round.

Students can strengthen their reports by citing reputable sources. For instance:

• The U.S. Department of Energy on LED lighting efficiency and applications
• NASA’s public materials on plant growth in space
• University horticulture or plant science departments explaining photoperiod and light quality

Using these references in your background research section shows that your project is built on the same ideas scientists are investigating at a larger scale.

FAQ: Examples of common questions about light and plant growth projects

Q: What are some simple examples of investigating plant growth rate under light for middle school?
Simple examples include comparing plants in full sun vs. shade, testing different window directions, or growing plants under a basic LED bulb vs. a fluorescent bulb. These setups need only basic supplies and still show clear differences in growth.

Q: Can I use colored plastic wrap instead of colored lights as an example of a light project?
Yes, this is a classic example of a low‑budget experiment. Students can cover separate plant groups with red, blue, or green plastic film and compare growth rate. The results are usually less dramatic than with actual colored LEDs, but they still provide examples of how light filtering affects plant development.

Q: What is an example of a good data table for a plant light experiment?
A solid example of a data table includes columns for date, light treatment (for example, red LED, blue LED, white LED), plant ID, height, leaf number, and any notes on color or wilting. This structure makes it easy to graph growth rate under each light condition later.

Q: How long should I run an experiment on plant growth rate under light?
Most school‑level experiments run for three to six weeks. Fast‑growing plants may show measurable differences in growth rate under different light conditions in as little as two weeks, but a slightly longer run gives better data.

Q: Are there examples of high school‑level projects on plant growth and light that use statistics?
Yes. High school students can run multiple replicates per treatment (for example, 10 plants per light type) and then use basic statistics, such as averages, standard deviation, and simple t‑tests, to compare growth rate. Many high school biology courses introduce these tools, and they fit perfectly with plant light experiments.

By using these examples of investigating plant growth rate under light as templates, students can design projects that are realistic, data‑driven, and grounded in modern plant science.