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12.2: Seedless Plants

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    Seedless Plant Lab

    Introduction

    Three major groups of land plants, Bryophytes, Lycophytes, and Ferns, are called seedless plants because they do not produce seeds (an adaptation that developed in later groups). A commonality of seedless plants is that they produce flagellated sperm, which require the presence of water to successfully fertilize an egg. For this reason, seedless plants are not as well-adapted to terrestrial life as more recently evolved groups.

    Bryophytes, a gametophyte-dominant group of plants, includes the mosses, liverworts, and hornworts. These plants are seedless and lack vascular tissue as well as true leaves, stems, and roots.

    Lycophytes, which includes club mosses, spike mosses, and horsetails, are a sporophyte-dominant group. Lycophytes are the first group of land plants to possess vascular tissue and true plant organs (roots, stems, and small leaves called microphylls).

    Ferns are the third major group of land plants to evolve. They are sporophyte-dominant and possess vascular tissue. A notable trait that evolved in the ferns is megaphylls, large leaves that enhance the plant's ability to absorb solar energy.

    In this portion of the lab, you will be observing examples of the three groups of seedless plants (bryophytes, lycophytes, and ferns). As you observe the specimens provided and describe the life cycles for each, think about the similarities and differences you see in the three groups.

    Lab Objectives

    At the conclusion of the lab, the student should be able to:

    • Explain what is meant by “alteration of generations”
    • Explain the difference between the sporophyte and gametophyte generation in plants. State which generation is haploid and which is diploid
    • Name the process that makes spores and state if spores are haploid or diploid
    • Name the process that creates sperm and egg from spores and state if sperm and egg are haploid or diploid
    • Name the phyla discussed in the lab and give an example of a plant from each
    • Identify and know the function of the archegonium and the antheridum
    • Identify the fern structures discussed
    • Understand the seedless plant life cycle

    Bryophytes

    Phylum: Bryophyta (Mosses)

    1. Observe different kinds of moss on display and note the body form of the gametophyte.
      Figure 1. Moss growing on a rock.
      Figure \(\PageIndex{3}\): Moss growing on a rock.
    2. Obtain live sporulating moss (if available) and identify the sporophyte and gametophyte generations.
      1. Is the green “leaf-like” tissue the gametophyte or sporophyte?
      2. Is the stalk that emerges from the green “leaf-like” tissue the gametophyte or sporophyte?
    3. Figure 2. Moss gametophytes and sporophytesFigure \(\PageIndex{4}\): Moss gametophytes and sporophytes
    4. Draw the life cycle of a typical bryophyte such as moss. Your drawing should contain the following terms:
      1. 2N (Diploid)
      2. N (Haploid)
      3. Sporophyte
      4. Sporangium
      5. Meiosis
      6. Spores
      7. Gametophyte
      8. Antheridium
      9. Sperm
      10. Archegonium
      11. Egg
      12. Fertilization

    4. Is the archegonium male or female?

    5. What cell is produced in the archegonium?

    6. Is this cell haploid or diploid?

    7. Is the antheridium male or female?

    8. What cell is produced in the antheridium?

    9. Is this cell haploid or diploid?

    10. Observe a slide showing the antheridial head of a moss. Begin using the scanning (4X) objective and then switch to the low-power objective (10X).

    11. What is produced in this structure (the antheridium)?

    12. Show where the antheridium occurs on the live moss plant. Indicate where this structure occurs in the life cycle diagram that you prepared (above).

    Figure 5. Mnium (a moss) antheridial head
    Figure \(\PageIndex{5}\): Mnium (a moss) antheridial head
    Figure 4. Mnium (a moss) antheridial head x40
    Figure \(\PageIndex{6}\): Mnium (a moss) antheridial head x40
    Figure 5. Mnium (a moss) antheridial head x100
    Figure \(\PageIndex{7}\): Mnium (a moss) antheridial head x100

    13. Observe a slide showing the archegonial head of a moss. Begin using the scanning (4X) objective and then switch to the low-power objective (10X).

    14. What is produced in the archegonium?

    15. Show where the archegonium occurs on the live moss plant. Indicate where this structure occurs in the life cycle diagram that you prepared (above).

    Figure 6. Moss archegonial head x 40
    Figure \(\PageIndex{8}\): Moss archegonial head x 40
    Figure 7. Moss archegonial head x 100
    Figure \(\PageIndex{9}\): Moss archegonial head x 100

    16. After the egg is fertilized, it grows and produces a sporophyte. A capsule containing a sporangium is found at the tip of the mature sporophyte. Refer back to Figure 2 on the previous page to view a sporophyte.

    17. What is produced within the sporangium?

    18. Be sure that you can identify the sporophyte and the sporangium on the live moss plant. Indicate where these structures occur in the life cycle diagram that you prepared (above).

    19. How are moss spores dispersed to new locations?

    Figure 8. Moss capsule containing spores
    Figure \(\PageIndex{10}\): Moss capsule containing spores
    Figure 9. Moss capsule x40
    Figure \(\PageIndex{11}\): Moss capsule x40

    Phylum: Lycophyta

    Members of this phylum have horizontal stems, upright stems, and small, spike-shaped leaves called microphylls.

    Club Mosses

    Observe a specimen of live club mosses such as Lycopodium. Find rhizomes. Identify microphylls. Do the specimens have any strobili? (Be sure to look up these words if you do not understand them.)

    Figure 17. Club moss (lycopodium)
    Figure \(\PageIndex{19}\): Club moss (lycopodium)

    Spike Mosses

    Observe a specimen of a spike moss such as Selaginella. Note the structure of the microphylls.

    Figure 18. Spike moss (selaginella)
    Figure \(\PageIndex{20}\): Spike moss (selaginella)

    Horsetails

    Observe a live horsetail if available. Find the a strobilus. What reproductive structures are contained within the strobilus?

    Figure 15. Horsetails
    Figure \(\PageIndex{17}\): Horsetails
    Figure 16. Horsetail showing strobilus
    Figure \(\PageIndex{18}\): Horsetail showing strobilus

    1. Observe the lycophyte slides provided to you. Begin using the scanning (4X) objective and then switch to the low-power objective (10X).

    Note

    The life cycles of lycophytes are very similar to that of bryophytes.

    Phylum: Pterophyta (Ferns)

    Figure 11. Fern gametophyte
    Figure \(\PageIndex{13}\): Fern gametophyte
    1. Draw the life cycle of a fern. Your drawing should contain the following terms:
      1. 2N (Diploid)
      2. N (Haploid)
      3. Sporophyte
      4. Sorus
      5. Sporangium
      6. Meiosis
      7. Spores
      8. Gametophyte
      9. Antheridium
      10. Sperm
      11. Archegonium
      12. Egg
      13. Fertilization

    2. Observe sori on the underside of a fern leaf. Are sporangia visible? Indicate where this structure occurs in the life cycle diagram that you prepared (above).

    Figure 12. Fern showing sori on underside of leaf
    Figure \(\PageIndex{14}\): Fern showing sori on underside of leaf
    Figure 13. Fern sorus x40
    Figure \(\PageIndex{15}\): Fern sorus x40

    3. Is the frond sporophyte or gametophyte?

    4. What cell is produced in the sori?

    5. Is this cell diploid or haploid?

    6. View a slide of a fern gametophyte showing antheridia. What reproductive cells are produced by gametophytes? Indicate where the gametophyte occurs in the life cycle diagram that you prepared.

    Figure 14. Fern prothallium (gametophyte)
    Figure \(\PageIndex{16}\): Fern prothallium (gametophyte)

    7. View the display that includes the fern prothallus.

    8. What shape is the prothallus?

    9. Is the prothallus part of the sporophyte or gametophyte generation?

    10. What reproductive structures are present on the prothallus?

    11. What cells are made in the archegonium?

    12. What cells are made in the antheridium?

    Follow-Up Questions
    1. Is gametophyte tissue haploid or diploid?
    2. Is sporophyte tissue haploid or diploid?
    3. Is the moss life cycle gametophyte or sporophyte dominant?
    4. Is the lycophyte life cycle gametophyte or sporophyte dominant?
    5. Is the fern life cycle gametophyte or sporophyte dominant?
    6. In the life cycle of plants, the process of meiosis produces what type of cell?
    7. Does the gametophyte or sporophyte generation produce spores?
    8. Which type of cell division is used to produce gametes in plants? How is this different than animals/humans?
    9. State one reason why bryophytes, lycophytes, and ferns are considered primitive plants.
    10. What is meant by the idea of “alteration of generations?”

    Contributors and Attributions

    CC licensed content, Original
    • Seedless Plants (Kingdom: Plantae), Biology 102. Authored by: Michael J. Gregory, Ph.D.. Provided by: LibreTexts. Located at: bio.libretexts.org/Under_Construction/BioStuff/BIO_102/Laboratory_Exercises/Seedless_Plants. Project: The Biology Web. License: CC BY-NC-SA: Attribution-NonCommercial-ShareAlike

    This page titled 12.2: Seedless Plants is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Lynette Hauser via source content that was edited to the style and standards of the LibreTexts platform.