1) How Roots Work
When explaining how roots work, it is helpful to demonstrate using a carrot. Slice the carrot both lengthwise and across to illustrate the stele.
2) Seed Germination
Give students a choice of seeds to germinate that includes a mixture of monocots (e.g., grass, corn) and dicots (e.g., lettuce, radish). Each student should randomly choose two species and place approximately 10 seeds of each in a petri dish lined with filter paper. The student should add water with a plastic squirt bottle. (The instructor might have to add more water over the next 7–10 days.)
Bring the germinated seeds back to class for students to observe. Allow groups of students to consider these questions, and then discuss them as an entire class:
- Using the drawings in Figure 4.6, try to determine which of your germinated seedlings are dicots and which are monocots. Is there one cotyledon (seed leaf) or two? Is there a main tap root or several random adventitious roots? The instructor can then have the groups report back their observations and list on a blackboard which seedlings are monocots versus dicots.
- Do you think the seedling produces the roots or the leaves first? Why?
- Why do you think that sprouts (germinated seeds) are more nutritious to eat than seeds? What kinds of sprouts have you eaten? Are there diseases of sprouts?
- Can you see the root hairs on any of the roots? What is the function of the root hairs?
Added Activity During the Seed Germination Discussion:
Most students living in northern areas do not know how peanuts grow. Bring in roasted peanuts in the shell (if there are no allergic students), and hand them out. Ask students if peanuts are monocots or dicots, and then ask how peanuts grow. Compare peanuts to peas and beans, which are likely to be familiar. Then ask how peanuts can grow in the ground if they are the seeds of a legume plant. Use a diagram or photograph to explain it.