Food Science Project

A bioassay is the scientific term for using a live organism to test the environment for toxicity. Many people recognize the term as “the canary in the coal mine.” Canaries are more sensitive to methane than humans. It is odorless, but deadly to both species. Canaries were taken deep within the mines, sometimes so deep that only the smallest of men and children could go. If the canary died, the men and children knew they’d better come up for air, or that would be their fate too.

No kidding.

Let’s hope we can predict our harmful toxins with more accuracy today. As a side point, when the hills of Pennsylvania were being mined for their coal in the early 1900s, life was plentiful, and the owners of the mines considered it cheap. They’d bring the dead bodies of workers back from mine accidents and just throw them off the cart and move on to the next family’s porch.

Today, let’s use lettuce, an innocuous species, and very sensitive to toxins, to test for toxins in our environment. There’s a controversy these days about whether or not our advanced farming methods are creating conditions that could lead to the Great Potato Famine of 1850. Scientists and laypeople alike question whether it is really necessary to modify and explore all the possibilities nutrients today in the way that food scientists and geneticists do today. Since these topics slice through biodiversity on their way through ecology, they are much too broad to narrow down into one subject. Lettuce is green, and it grows on the earth, which sort of makes it fit in both parameters, including another one about food. By the way, did you know that grasses are the most common vegetation on the earth?

Anyhow, now that we’re back on the earth, let’s just do a simple bioassay testing either the soil for herbicide runoff if it’s summer, or ice melt runoff if its winter.

Step 1. Obtain Buttercrunch Lettuce seed, if at all possible.

Step 2. Mix a ten percent bleach solution by mixing one part bleach to p parts distilled water. Soak the seeds for 20 minutes in this. Then rinse with water five times. Using this bleach mix kills fungal spores, which can interfere with germination. If you use tap water, you’ll have more variables because the tap water contains unknown minerals at the least.

Step 3. Hopefully you will have already gathered your soil samples. Place 3 grams of the sample in the bottom of three Petri dishes and cover with filter paper. If the filter paper doesn’t get moist, add up to 2 ml of distilled water.

Step 4. Set up a control test with three dishes with filter paper on top, and up to 2 ml of distilled water.

Step 5. Add five lettuce seeds, spaced so that they do not touch each other or the sides of the dish to all the Petri dishes.

Step 6. Place them in a plastic bag, seal it, and incubate in the dark at about 24.5 degrees C for 5 days (120 hours).

Step 7. At the end of five days, count how many seeds have germinated. Measure the length of each root to the nearest mm. The root will have little hairs coming out of it. Do not include the shoot in this measurement.

Interpret the results. What can you deduce from the results?

Check out the seeds in the distilled water first. Probably not all of them germinated. That’s just the way it goes, as any good gardener knows. Even Jesus didn’t get perfect results when he sowed seed.

If less than 80% of the (5x3) sprouted, something went wrong in the control group. Blame the seeds first. They might have been old, dried out, poorly stored, etc. Maybe the dog got in and sucked up all the water. Your kid brother turned up the temperature. You forgot to check the critter for, what, a month. Go back to jail, do not pass go; do not collect one hundred dollars. Begin again I mean to say. Even if everything else went right, if you used tap water, you could change the name of the experiment, and say you were testing the local tap water, and then do the same test with some other location’s tap water …

If a sufficient number of seeds sprouted in the control group, now look at the group of seeds from the sample group.

Now is you turn to evaluate the facts. Does this experiment appear replicable? Are some results sketchy, influenced by an unknown variable perhaps? Should it be run again? At this point, things should be pretty uniform within the two classes, if not between them.

Your call, scientists. You’re on your way.