From Seed to Seed:
Plant Science for K-8 Educators

 

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Activity 21: Plants That Bite Back

Grades: K-4

Associated Lesson Topics:

  • Adaptations for nutrient uptake
  • Carnivorous plants

National Standards:

Planting the Seed...

What do you think plants need to survive? Do plants need food? Where do you think they get their food? Do all plants get their food through photosynthesis?

Teacher Information:

This activity provides an opportunity to explore the needs of plants and the adaptations that enable them to meet their requirements. Plants need water, air, light, and nutrients. What does a plant do if one or more of these requirements are not met? While some plants suffer or die, others can adapt to these situations. Bog plants offer an excellent example of those that are able to adapt.

A bog is a type of wetland. The difference between a "typical" wetland and a bog is that bogs are stagnant. In other words, the inflow and outflow of water is restricted. Bog vegetation is dominated by sphagnum moss, sedges, and rushes. These plants form a mat of vegetation that prevents sunlight from reaching the stagnant water. As a result, algae and other aquatic plants are unable to grow and produce oxygen. Bogs are also acidic. Sphagnum moss accumulates carbon ions and, in return, releases hydrogen ions. The release of hydrogen ions decreases the pH of bogs, causing them to be acidic. The inadequate supply of oxygen combined with high acidity produces a mineral-deficient atmosphere because bacterial decomposition of organic matter is impeded. As a result, bog plants have to get their nutrients from somewhere other than the soil.

"Carnivorous" plants are specially adapted to grow in bogs. Instead of retrieving their nutrient supplies from the soil, they have developed elaborate traps to lure insects. Instead of animals eating them, these plants eat animals!

We've included this detailed information for your benefit. To delve into carnivorous plants with your students, simply begin by growing some.

Necessary Materials:

  • Carnivorous plants. We recommend purchasing Venus flytrap (Dionaea muscipula), sundew (Drosera spp.), bladderwort (Utricularia spp.) and/or pitcher plant (Sarracenia spp.) seedlings.

Procedure:

  • Purchase carnivorous plants. Before planting them, consider that such plants require oxygen-depleted, nutrient-poor soils to thrive! Therefore, plant them in non-porous soil (e.g., clay, peat) and rarely, if ever, fertilize them. If you are growing these plants in the classroom, it is a good idea to enclose them in a terrarium or miniature greenhouse (which students can build from old wire hangers and plastic wrap) to prevent their insect dinners from escaping! These plants require insects only once or twice a month. Overfeeding can kill them.
  • An alternative is to build a model bog habitat. Directions for building a bog are included in Activity 22 (All Bogged Down). The directions are for building a classroom bog model. However, you and your class can make adaptations to build a bog in your schoolyard.

Harvesting the Crop...

Without letting on, have your students observe these plants. It can be an exciting surprise to see a flytrap snap shut around a fly! Once they have observed the techniques that these plants use to lure and eat insects, have a discussion about carnivorous plants. Why do these plants eat insects? What are the insects providing for the plants? Why don't all plants eat this way? We guarantee they will never forget this experience!

Sources

 

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