brassica rapa: modeling growth

Thanks to pure serendipity, one of my projects at school focuses on how kids learn about evolution through scientific modeling and observation. Students grow plants in their classrooms, measure the plant growth and build models (e.g. graphs etc.) to analyze their data. To simulate the experience of students (since our team is far from the classrooms where the project is based) we decided to grow the same plants as the students and measure the growth ourselves.

In the video game age, kids have short attention spans. So some botanists at the University of Wisconsin bred a quick-growing plant for use with kids. They aptly named the plant: Wisconsin Fast Plants (species: brassica rapa). We ordered a kit that comes with soil, seeds, fertilizer and a host of other materials to get you on your way (including a plastic "light box" that shines fluorescent light on the plants 24/7.) Here is our set of Fast Plants after about 3 days:


Yesterday, when we measured the plants (Day 28), some of the tallest plants had grown to almost 30 centimeters. They don't grow straight up, making it hard to measure. But they do have pretty little yellow flowers. We pierced a dead bee (they came with the kit) with a skewer and simulated pollination, rubbing the bee up against different yellow flowers. Pollen sticks to the bee's hairy body and the bee inadvertently spreads the pollen to different flowers while looking for nectar. This fertilization allows the plant to produce seeds.


Of course kids also like observing caterpillars and butterflies, so we ordered some Cabbage White butterfly eggs (species: pieris rapae). Concerned that the eggs would hatch into ravenous caterpillars that would destroy our baby fast plants, I put the eggs in a jar with some cabbage. A few of the eggs hatched and the baby caterpillars ate a lot of cabbage...and they also produced a lot of frass (caterpillar waste.) Frass gets moldy after a while (yuck!) so today I cleaned out the jar and added fresh local cabbage from our CSA (Community Supported Agriculture.) I managed to salvage a little bit of non-moldy frass to use as fertilizer for the plants. As I cleaned out the jar, I was saddened to find only one healthy caterpillar remaining! We'll take good care of him, and as soon as he pupates, we'll move him into the light box with the brassica rapas.