Number of Seeds Effect on Plant Height (Janica Henzie)

Research Question and Hypothesis

Question: How does the number of seeds planted affect the average plant height?

Hypothesis: As the number of seeds planted increases, the average height of the plants will decrease.

Standards

7.7.a. Select and use appropriate tools and technology to perform tests, collect data, and display data.

8.9.a. Conduct and plan a scientific investigation to test a hypothesis.

8.9.e. Construct appropriate graphs from data and develop quantitative statements about the relationships between variables.

Experimental Design

Pinto bean seeds were used. They were soaked for several hours before planting. Seeds that were cracked were not chosen. Small plastic drinking cups were used for pots - holes were punched out of the bottom to allow for drainage. The following were the groups: 1 seed, 2 seeds, 4 seeds and 8 seeds. There were two groups (box 1 and box 2). All seeds were planted at the same depth; they were given the same soil water, etc. The only difference was the number of seeds planted in each cup.

Independent variable

The independent variable is time; measured every day.

Dependent variables

The dependent variable is the average height of the plants. The height of the plants were measured by using a metric ruler and using centimeters (cm). The ruler was placed on the soil and the highest, unsupported plant height was measured. The average height of the plants in the cup was then calculated.

Series

Study the height of plants as a function of the number of seeds planted per cup at various times.

Constants and Controls

Constants: all variables were controlled and kept the same between the groups (type of seed, type of soil, amount of soil, type of pot, environment (temperature, water, light)).

Control: pots with only one seed planted would serve as the control

Materials

Pinto bean seeds (supermarket)
plastic cups (supermarket)
soil (home garden store)
water (any working faucet)

Procedures

Soak pinto bean seeds in a cup of water for 3 hours.
Prepare cups to be used as pots by punching three holes in the bottoms of at least 4 cups. Fill cups with soil and then water soil so that it is damp. Label cups: 1, 2, 4, and 8.
After the seeds have soaked, spread them out on the counter. (Before spreading the seeds, skim off any seeds that were floating at the top of the water and throw away). Select seeds to plant (do not choose seeds that have cracked).
Using a finger to create a hole in the soil, create a depression about 5 cm deep in the cup labeled 1. Place one seed in the depression and cover with soil. Set aside.
Repeat step 4 for each cup by making the number of depressions for the number of seeds to be planted in that cup (2, 4, and 8 seeds respectively).
Allow time for the seeds to grow. Do not water until the tops of the soil are dry. Keep the cups in the same location so that all cups receive the same temperature, light, etc.
Each day record the height of the plants by using a ruler in centimeters (cm). Do not support the plants when recording their heights. Calculate the average height of the plants in each cup.