Lab 4 – Experimental Setup

You will need to obtain the following resources –

• 8 identical cups (solo plastic cups work well, but mason jars/drinking glasses will also work)
• Potting soil
• Ruler
• Bag of dried pinto beans
• Green light bulb, and a lamp/light source to use it in (should be able to keep it in a dark place with only the green light lamp)
• Light source with a regular “white” light bulb that can be kept on 24/7 for two weeks.
• Liquid measuring cup (can also use dry measuring cups)
• Measuring spoons
• (Optional) Plate, tray, or baking sheet that you will not need for the next two weeks (to catch excess water/dirt spills)

Bean cup (“pot”) setup – Separate your cups into two groups of four – one for white light, and one for green light. Label the cups #1 – 4 and the color of light they will receive. Fill each “pot” cup with 1 + ½ cups of soil. It may be a good idea to place cups on a plate or rimmed baking sheet to minimize chance of mess/leaking. Make shallow depression (~1 cm deep) in the middle of the soil in each pot and place 5 beans inside. Beans do not have to be in a single pile, but can be spread throughout the top of the soil (still ~1 cm deep). Cover with soil. Repeat for all 8 cups.

Green & white light setup – The goal is for your beans to only receive the color of light assigned to that group, which is to say, you are controlling for wavelengths of light that your beans receive. You will set up two light treatments – green light, and white light. Because white light is the color of a regular light bulb, the white light experimental setup is generally easier, because most people already have a good place (like a bathroom, or a spare/guest room in your house/apartment that is not used all the time) where they can keep a light on 24/7 for the two week duration of this experiment. The other setup can be another light fixture (like a bathroom) with just a green lightbulb, or it can be a lamp. Although the locations of the experimental setups will be different, there are three important things to note –

1. The green and white bean-growing experiments must be done at the same time
2. The distance between each light source and the bean cups must be roughly the same (can very ~5 cm in either direction)
3. Lights must remain on 24/7 for the next two weeks (during data collection)
4. The color of the treatment (green or white light) should be the ONLY light that your beans receive for the duration of the experiment.

Light location – Basements, bathrooms, rooms, and closets with no windows are ideal. Do the best that you can to make sure that your beans are only receiving light from your lamp and no light from other sources (as you are attempting to control for light wavelength) and remember that if you are using a lamp, they require an electrical outlet and you will need to access your plants every day for the next two weeks to take measurements.

When setting up your lamp, remember that the hood/lightbulb of the lamp may get hot. If using lamps – Do not cover the lamp with anything (especially cardboard boxes), as this is a fire hazard. Do not operate the lamp in close proximity to vehicles or any flammable vapors or liquids (a garage or shed is not a recommended location to set up your experiment).

This experiment is designed with the expectation that the lamp will be on 24/7 for the duration of the experiment. Once turned on, do not unplug or turn off the lamp until the experiment is complete. Let others in your household know, so that they do not accidentally turn off your lamp.  

Helpful notes – If you do not have a lamp but do have two places to leave lightbulbs on 24/7 (for example, two separate bathrooms), this is acceptable. Clamp lamps work very well in this experiment, because they can be clamped to other objects, or held by a stack of heavy books at a specified height.

Watering – Starting on Day 0, you will need to water each bean cup with 3 teaspoons of tap water every 4 days (so the next time you water them is on Day 4).

Data notes – Along with your data, keep a list of observations (these will be so helpful with your lab report later on!). Make note of things like “My mom accidentally turned off my lamp for two days, so the plants did not receive light for that time”, or “My cat knocked over the bean cups, so I restarted the experiment on Day 4”. If you would like, you can take pictures of the experimental setup throughout your experiment to include in your lab report.

Data collection

The day that you set up your bean cups is Day 0. You will collect data every day starting on Day 1. Data collection ends on Day 14. Every day you will measure:

• The number of beans that have sprouted in each bean cup
• The height of all bean sprouts in cm (not just the tallest one!)

Note: Your measured bean height is not specific to each sprout (it is specific to each bean cup).

Data should be collected using the Excel sheet provided to you on Sakai. Table 4.1 is included as an example if you would like to print data sheets and later input your data to the Excel sheet. If you are printing sheets, you will need eight copies of Table 4.1 (one for each bean cup). You will need a digital version of your data for Lab 6, and will turn it in as part of the Lab 6 assignment.