Lab 5: Seed-bearing Plants
Materials needed
Sharp knife
Cutting board
Large pine cone with open “scales”
Fascicle (bundle) of pine needles
2 household cups (may be disposable)
Measuring cup
Red food coloring
Blue food coloring
Salt
Celery stalk
Pea pod: sugar snap pea or snow pea
Dry lima beans (3)
Activity: anatomy of pine
1. Obtain a pine cone and a fascicle (bundle) of pine needles. Refer to Figure 5.1 as you perform this activity.
2. Examine the fascicle of pine needles (Figure 5.1). A pine needle is actually a leaf. It has green pigmentation for photosynthesis. It is skinny, leathery, and coated with a sticky resin to help retain water. Pine needles are bound together in a bundle (fascicle). Different species have different numbers of needles per fascicle. For example, white pines (Pinus strobus) have five needles per fascicle, while red pines (Pinus resinosa) have two needles per fascicle.
3. Examine the large pine cone (Figure 5.1). It should be large enough to fit into your palm, andits woody “scales” should be open. Pine trees produce two kinds of cones: pollen cones and seed cones (or ovulate cones). Pollen cones are small – they often are not much bigger than the last digit of your pinky finger. These cones produce pollen grains, which contain sperm. You should have a larger cone, the seed cone. Each woody “scale” of the seed cone typically produces two eggs at its base. Before the eggs are fertilized, the seed cone is closed up. Pollen grains blow into the cracks between the closed scales, and fertilize the eggs. The fertilized egg then develops into a seed, and the scale opens. The scales are called sporophylls (“spore” + “leaf”).
4. Break off a few scales near the top of the cone. Examine the base. You should see two indentations where the seeds used to be. Examine or break off a few scales near the bottom of the cone. There may be seeds present (Figure 5.1). The pine seed has a “wing.” This enables the seed to disperse away from the parent plant via the wind. This is why the scales open up once the seed develops.
5. A seed cone usually does not release all of its seeds at once. Thus, part of the cone, usually the top, is often more “open” than other parts. Because pine cones rely on the wind to disperse seeds, it is important that the “wing” of the seed stays dry. Pine cones protect developing seeds from becoming waterlogged through a passive reaction.
a. Place your open seed cone into a cup of tap water.
b. Record: Time into water _________
Describe your observations and any changes in the cone appearance
c. Let the cone sit in the water for at least 30 minutes.
d. Record: Time out of water _______
Describe your observations and any changes in the cone appearance
