Seed-bearing Plants

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

Fig 5.1

Lab Report

This is an experimental variation on the celery food dye activity of Lab 5.

Activity

1. Obtain four cups (two of which could have been used in Lab 5). As in Lab 5, fill each cup with 400 ml of tap water. Use red dye to darkly stain two cups, and use blue dye to darkly stain the other two cups. Be sure that each red cup gets the same amount of dye and that each blue cup gets the same amount of dye. Record the drops in each. Add a spoonful of salt into each cup.

2. Label one red dye cup and one blue dye cup with an S (high salt). Add 4 spoonfuls of salt to each of these cups. Stir the solutions thoroughly.

3. Obtain two similar stalks of celery, each with some leaves at the top. Cut a 1-cm piece (about one-half inch) off the bottom of each stalk. Keep the relative lengths of the two stalks as similar as possible.15

4. Carefully, split the stalks up the middle about half-way. The stalks should each now have two “legs.” Be sure that the legs of each stock are similar sized (i.e., the left leg and right leg are the nearly the same length and width).

5. Place the red S cup and the blue S cup together. Gently place one “leg” of one stalk into the red S cup, and the other “leg” of the stock into the blue S cup. The celery should now be “straddling” the two S cups (Figure 5.2.B). Place the red non-S cup and blue non-S cup together and situate the legs of the other celery stalk into each cup (i.e., the celery “straddles” these two non-S cups).

6. Record the time at which you place each celery into the pairs of cups as “Start time.”

	Start time	Stop time
a. S cups (high salt)
b.Non-S cups (low salt)

7. Let the celery sit in the cups for 6 hours, or until you can see color in the leaves of one of the stalks. In Step 6 above, record the time when you remove the stalks as “Stop time.”

8. Examine the top of the celery stalks. Are there differences between the celery in the high salt (S) and low salt (non-S) water conditions? Record your observations in Question 1 of Lab Report 6.

9. Remove the celery from the cups (be sure to keep it clear which came from the high salt solution (S) and which came from the low salt (non-S) condition). Lay each stalk out flat. Starting at the top, move down the stalk, making cross-sectional cuts. Stop when you first see evidence of dye. Measure how far up each stalk the red and blue dyes climbed. In Table 6.1 in Lab Report 6, record the distance (cm) traveled by the red dye in high salt conditions (S), the blue dye in high salt conditions (S), the red dye in low salt conditions (non-S) and the blue dye in low salt conditions (non-S).

10. Tear apart the celery stalk. Notice the feel of the vascular tissue, and how the food coloring lies within it.