Week 6: Nonvascular Plants and Seedless Vascular Plants

I. Kingdom Plantae: Origin and Phylogeny

Plants evolved from green algae (Supergroup Archaeplastida) approximately 470–480 million years ago. The nearest living relatives of the plant kingdom are a group of green algae called charophyceans or charophytes (Phylum Charophyta). A common charophyte is the stonewort. There are over 700 species of charophytes, most of which live in fresh water habitats such as ponds and streams (see Figures 1A and 1B).

Activity 1: Overview of Plant Classification

Plants can be classified into three basic groups: nonvascular plants, seedless vascular plants, and seed plants. Find each of these groups in Figure 2 below.

Your instructor may ask you to review “Reading: Seedless Plants” before coming to lab. You will also find links to this reading in the paragraph below on plant classification.

Plant taxonomy

Fill in a table like the one below, using the information from “Reading: Seedless Plants” (scroll down to the table in the section labeled “Classification”). This will tell you the names of the phyla in each group, as well as the common names for each phylum. To find the characteristics, read “Bryophytes” for nonvascular plants and “Seedless Vascular Plants” for seedless vascular plants. If you cannot find information for each subgroup, that is OK—just be sure to include characteristics for each of the following groups: nonvascular plants, seedless vascular plants, seed plants, gymnosperms, and angiosperms. The first one is done for you as an example.

Plant kingdom phylogeny

To show the evolutionary relationships of the major plant groups, we can create a phylogenetic tree, as you have done in earlier labs. For those trees, you used DNA evidence. This week, you will use the characteristics from the table you completed above to determine relatedness and then construct a tree. Your tree should include the following groups: nonvascular plants, seedless vascular plants, seed plants, gymnosperms, angiosperms, monocots, and eudicots.

Activity 2: Alternation of Generations

Before lab, watch the following video for an explanation of the “alternation of generations” life cycle if you need a review. You don’t need to watch the first half of the video—you can start watching at 4:12 and continue to the end (about five minutes total). Refer to Figure 3 (below) as you watch, relating the explanations in the video to the diagram.

Study Figure 3 below, which depicts the general life cycle of plants. As you may know, plants have a life cycle that alternates between a haploid stage, called the gametophyte, and a diploid stage called the sporophyte. For most plants, we usually see only the sporophyte stage. The gametophyte stage is often tiny and contained deep inside the tissues of the sporophyte stage. Understanding this life cycle is an important tool for understanding the evolution and classification of plants.

Now play “Alternation of Generations,” a game testing your knowledge of the life cycle of plants. IMPORTANT: Click on the triangular play button on the diagram. Do not click on other buttons labeled “start” or “download”—these are ads trying to add an extension to your browser (and it can be hard to remove it). The game should take you about 5–10 minutes. See how fast you can get all the answers correct! Take a screenshot of your best time and paste it into your lab report.

Activity 3: Life Cycle of the Moss

Watch the video “Examine metagenesis and the roles of antheridia, archegonia, and the sporangium in the moss Mnium hornum.” Afterward, download and print out a copy of Figure 4 and then label the diagram using the following terms: gametophyte, sporophyte, capsule, spores, germination, protonema, antheridia, archegonia, and fertilization. Note that not all terms correspond to one of the numbers 1–6 in the diagram..

Key Terms

II. Nonvascular Seedless Plants

Before lab, review “Seedless Plants Bio II Slides,” which highlights the characteristics of nonvascular and seedless vascular plants.

This week we are focusing on nonvascular plants and seedless vascular plants. A familiar example of a nonvascular plant is moss, such as the plant shown in Figure 5 below.

Activity 4: Microscopic Survey of Nonvascular Seedless Plants

Observation of prepared slides—Bryophytes

Proceed to the demonstration table to obtain the prepared slides of the Bryophytes listed below. Please, perform microscopy observations, and write your observations in your lab notebook.

• Phylum Hepatophyta: Liverworts (slides)
  • Marchantia antheridia
  • Marchantia archegonia
  • Marchantia sporophyte
• Phylum Bryophyta: Moses and Polytrichum (slides)
  • Moss antheridia
  • Moss archegonial
  • Moss sporangium (capsule)
  • Moss protonema

Answer the following questions (many of which are adapted from the source attributed below).

1. What are the characteristics of nonvascular plants?

2. As indicated in the reading, use the space below to draw a simple life cycle of the moss. Include in the life cycle 2N, N, sporophyte, gametophyte, meiosis, spores, egg, sperm, antheridium, archegonium, and fertilization.

3. View the prepared slide of the archegonium and the antheridium. Is the archegonium male or female?

4. What cell is produced in the archegonium?

5. Is this cell haploid or diploid?<

6. Is the antheridium male or female?

7. What cell is produced in the antheridium?

8. Is this cell haploid or diploid?

9. View the prepared slide of the moss capsule. Is the capsule sporophyte or gametophyte tissue?

10. What cell is produced in the capsule?

11. Is this cell haploid or diploid?

12. How are moss spores dispersed to new locations?

Making a wet mount of Chara or Nitella

On your lab bench, you will find the following materials:

• glass slides
• cover slips
• lens paper
• dropper bottle of water
• dissecting needle

To prepare a wet mount:

1. Obtain a clean slide and draw a circle using the red pencil provided.
2. Use the forceps or dissecting needle to remove a piece of the Chara or Nitella.
3. Place the Chara or Nitella sample into the middle of the circle that you have drawn.
4. Use the Pasteur pipette, and place a small drop of water onto the sample.
5. Make sure that the water is evenly spread over the sample.
6. Once your sample is completely covered, gently place the coverslip over the top of the sample avoiding any air bubbles.
7. Observe your newly prepared wet mount under the microscope and record your findings in the lab notebook.

Answer the following questions (adapted from the source attributed below).

1. View the live moss specimens available in the lab. Is the green “leaf-like” tissue gametophyte or sporophyte?

2. Is the stalk that emerges from the green “leaf like” tissue gametophyte or sporophyte?

III. Seedless Vascular Plants

Before lab, read the information on the seedless vascular plants in “Seedless Vascular Plants.” and review “Seedless Plants Bio II Slides.”

A familiar example of a seedless vascular plant is a fern, such as the plant shown in Figure 6 below.

Activity 5: Microscopic Survey of Seedless Vascular Plants

Proceed to the demonstration table to obtain the prepared slides of the Lycophytes and the Pterophytes listed below. Please, perform microscopy observations, and write your observations in your lab notebook.

• Phylum Monilophyta:
  • Subphylum Sphenophyta: Horsetails
    • Equisetum (living plant)
    • Equisetum (slide)
  • Subphylum Pterophyta:
    • Fern slides
      • cycle
      • prothallium
      • sporophyte

Answer the following questions. Use “Seedless Plants Bio II Slides” for help. (Questions are adapted from the source attributed below).

1. What are the characteristics of seedless vascular plants?

2. Draw a simple life cycle of the fern. Include in the life cycle 2N, N, sporophyte, gametophyte, meiosis, spores, egg, sperm, antheridium, archegonium, fertilization, and sorus.

3. Observe the preserved fern frond. Locate the sori on the underside. Is the frond sporophyte or gametophyte?

4. What cell is produced in the sori?

5. Is this cell diploid or haploid?

6. View the prepared slide of the fern prothallus under the microscope. What shape is the prothallus?

7. Is the prothallus sporophyte or gametophyte?

8. Can you find the archegonium and the antheridium?

9. What cell is made in the archegonium?

10. What cell is made in the antheridium?

IV. Post-lab Questions

To complete this lab and summarize what you have learned, please answer the following questions.

1. Visit the interactive fern life cycle at Science Learning Lab and use the interactive tool explaining the life cycle of a fern. Click on each label to see the details of each stage and each structure. Afterward, download and print out a copy of Figure 7 and then label the diagram by indicating the correct structure or phase of the life cycle for all of the following terms: sporophyte, gametophyte, spores, germination, rhizoids, sorus, frond, archegonium, antheridium.

2. Is gametophyte tissue haploid or diploid?

3. Is sporophyte tissue haploid or diploid?

4. Is the moss life cycle gametophyte or sporophyte dominant?

5. Is the fern life cycle gametophyte or sporophyte dominant?

6. In the life cycle of the primitive plant, the process of meiosis produces what cell?

7. Does the gametophyte or sporophyte generation produce spores?

8. What process do spores undergo to create sperm and egg?

9. State one reason why moss and fern are considered primitive plants.

10. What is meant by the idea of “alteration of generations?”

Attribution

Questions in this lab are adapted from “4.1: Seedless Plant Lab” by Lynette Hauser, licensed CC BY 4.0.