Science Models
Science Fair Projects

Published on Sep 05, 2023


How does caffeine influence soybean plant growth? The independent variable is the solution used to water the plants, which are water, caffeine solution and a coffee mixture. The dependent variable is the growth of the soybean plants. Coffee can certainly stimulate growth in plants, because of its high concentration inessential ingredients that promote plant growth that can be found in many commercial fertilizers.


1 packet of soybean seeds 3 gardening pots

Soil, no additives

Gardening utensils

Tap water

Caffeine tablets

Coffee powder

2 beakers

1 measuring cylinder

1 digital weighing scale

1 black marker

Planning the Procedure

1. Fill the three pots with equal amounts of soil. Plant ten soybean seeds in each pot and allow them to germinate. Additional seeds can be placed in the pots in case some of the seeds do not germinate; the additional plants can be removed later.

2. For the first 5 days, water the 3 pots with tap water only. Allow the seeds to germinate for the first 5 days.

3. After 5 days, measure the height of the 10 plants in each pot. Add up the individual heights and divide by 10 to obtain the average height. Record the average heights in a table, as shown below.

4. Prepare the caffeine solution by dissolving 10g of caffeine tablets in 100ml of water in a beaker. Label the beaker 'caffeine'. Similarly, add 10g of coffee to 100ml of water in another beaker and label it 'coffee'.

5. Label the 3 pots 'water', 'caffeine' or 'coffee'. Over the next 10 days, water the pots once a day with 100ml water, caffeine solution or coffee mixture, according to the labels on the pots.

6. Measure and calculate the average height of the soybean plants every day for the next 10 days.

Data and Graphs:

The results show that the soybean plants grew faster when they were watered using the coffee mixture, but the growth was slower when the plants were watered using the caffeine solution. Nonetheless, soybean plants that had caffeine additives grew faster than plants with no caffeine additives

Solution Height of Soybean Plants (mm)

...................Day 1    Day 2    Day 3    Day 4    Day 5    Day 6    Day 7    Day 8    Day 9    Day 10

Water           38      ....46      ..53      .....61         68      ....77       ....85        .92         99      ....107

Caffeine       37     .... 43      ..48      .....52         56      ....59       ...62        .65        ..68       .... 71

Coffee           39   .....  47       ..55     .... 63         72      ...81       ....92      ..102       .113      ....125

Scientific Explanation:

The hypothesis that soybeans watered using a coffee mixture will grow the fastest has been proven to be true. However, the effect of caffeine on plant growth is still a work in progress. Experiments on plant growth using only caffeine have resulted in the plant leaves becoming wrinkled, turning brownish and exhibiting deferred growth.

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