Download Lab 5: Plants: Nontracheophytes and Seedless Vascular Plants

Name: _________________________
Lab 5: Plants: Nontracheophytes and
Seedless Vascular Plants
Objectives:
• Name the major structures of a moss.
• Describe the life cycle of a typical bryophyte; distinguish between the
gametophyte and sporophyte generations.
• Become familiar with the major structures and life cycle of liverworts.
• Examine the vegetative and reproductive structures of the ferns
• Describe the life cycle of a fern; distinguish between the gametophyte and
sporophyte generations
• Distinguish between roots, rhizoids, and rhizomes
• Examine various structures and plants of the Phylum Sphenophyta
General Introduction:
Plants are generally defined as multicellular, photosynthetic eukaryotes. Plants cells have cell walls composed of
cellulose, and store surplus carbohydrates as starch. They utilize two photosystems in photosynthesis with two forms of
chlorophyll (a and b).This list of characteristics is not mutually exclusive to the Plant Kingdom however as several phyla of
algae (Kingdom Protista) also fit the description. Therefore, the definition of plants can be refined to include the fact that
plants enclose their embryos in parental tissue. (Whether looking at moss or ferns where the embryos grow directly on the
parental (haploid) gametophyte, or the seed plants where the embryos are enclosed by parental tissue in the seed.) The plants
are sometimes referred to as “embryophytes” due to this. The plants also show adaptations to a terrestrial life cycle as most
live on land. Aquatic plants are generally viewed as secondarily aquatic.
Plants live a life cycle referred to as “alternation of generations”. The key to this life cycle is that both the haploid
stage (gametophyte) and the diploid stage (sporophyte) are multicellular. The gametophyte produces haploid gametes
through mitosis and the sporophyte stage produces haploid spores through meiosis. As we examine the Plant Kingdom, you
should notice a shift in the alternation of generations from a gametophyte dominant life cycle (mosses and liverworts) to a
sporophyte dominant life cycle (ferns, conifers, and flowering plants). Importantly, remember that all the plants still exhibit
a true alternation of generations.
We will examine the Plant Kingdom through a series of 4 evolutionary stages. The nontracheophytes (mosses and
liverworts) exhibit the first stage: embryos wrapped in parental tissue. The second stage, formation of vascular tissue is
displayed in the vascular seedless plants (ferns and horsetails). Evolution of seeds is examined in the conifers, and the
evolution of flowers is studied in the anthophytes. The classification scheme used here is from Campbell and Reece 7th
edition.
General
1. Work in a group (the size of the groups will be determined by the size of the class and by the amount of equipment
available
2. Examine the slides (and demonstration slides) and the mold specimens provided in the lab.
3. Please do not hoard all slides or specimens at your lab station, and allow other students to have access to all slides.
4. Use the pictures in the photo atlas and your textbook to guide you through the slides and specimens.
Note: Some of these slides are difficult to interpret. Do your best and ask me if you have questions.
1) Nonvascular plants (Phyla Bryophyta and Hepatophyta)
Background: The nonvascular plants represent a group of plants that still display life before true vascular plants
evolved. Materials are still transported through the plant body, but the vascular cells of later plants are not evident.
Consequently, the nonvascular plants are generally low-lying, mat-like plants in which water is absorbed as much
through the “leaf-like” structures as it is through the rhizoids. The alternation of generations life cycle is very
evident as both the mutlicellular haploid gametophyte and the multicellular diploid sporophyte are visible and will
be viewed macroscopically in this lab. You will also examine the sexual reproductive structures (gametangia and
sporangia).
Define and/or recognize: gametangia (antheridium, archegonium), sporangia (capsule), gametophyte, sporophyte,
“leaves”, protonema
Bio 203: Lab 5: Plant Kingdom (Nonvascular and Seedless Vascular Plants)
Phylum Bryophyta (mosses)
Slides: Mnium or moss archegonial head (l.s.), Mnium or moss antheridial head (l.s.), Moss protonema (w.m.),
Mnium or Moss capsule (c.s.), Mnium life cycle, Moss gametophyte stem (c.s.)
Live specimens: Observe the various species (and life cycles) of moss
Models: Observe the three-part moss model. Identify (1) the antheridial (male) gametophyte, (2) the arcehgonial
(female) gametophyte with sporophyte, and (3) enlarged sporophyte capsule.
Plastic Mounts: sporophyte, archegonial (female) ganetophyte, antheridial (male) gametophyte
Phylum Hepatophyta (liverworts)
Plastic models and live specimens (if available): live specimens of liverworts (recognize the thallus, rhizoids,
antheridiophore, archegoniophore, and gemma cups)
2) Seedless vascular plants (Phyla Pterophyta)
Background: Vascular tissue is composed of cells joined into tubes transporting water and food nutrients
throughout the plant body. Xylem tissue is the water-transport tissue carrying water from the roots up the plant
body, and phloem tissue is the food-transport tissue carrying phloem sap (food nutrients) from food sources (leaves
or food storage organs) to food sinks (growing nonphotosynthetic structures or food storage organs). The bodies of
the vascular plants are divided into an aerial shoot system (stems, leaves, and reproductive structures), and a
subterranean root system. True leaves, stems, and roots all contain true vascular transport tissue. These plants are
seedless.
The alternation of generations is sporophyte dominant as the diploid plant is the most familiar plant body. The
sporangia (sori) produce spores through meiosis. Homosporous spores germinate into a haploid gametophyte that is
usually hermaphroditic (monoecious) with both antheridia and archegonia. The sperm cells are released and
“swim” to the archegonia to fertilize the eggs. Within the archegonia, embryos develop from the diploid zygote.
The embryos grow to sporophytes directly out of the gametophytes.
Define and/or recognize: sporophytes, sori, sporangia, strobili, vascular tissue, gametophyte, prothallus, antheridia,
sperm, archegonia, and eggs
Ferns
Slides: fern sporangia c.s., fern prothallus (antheridia and archegonia), fern prothallus (young sporophyte)
Demo Slide: Pteridium (fern) rhizome x.s.
Live or fresh specimens: fern sporophyte fronds, C-fern gametophytes
Plastic Mounts: Fern life history
Horsetails
Slides: Equisetum strobilus, l.s. and x.s., Equisetum sterile stem tip x.s.
Live specimens (if available): Equisetum sporophyte plants
Plastic Mounts: Equisetum sporophyte plants: vegetative & strobilus
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Bio 203: Lab 5: Plant Kingdom (Nonvascular and Seedless Vascular Plants)
Questions to Answer:
1.
Are the “leafy” (photosynthetic) portion of the moss of the sporophyte or gametophyte generation? What evidence
would you use to support your answer?
2.
Why is the moss life cycle considered a “gametophyte dominant alternation of generations” and not a “haploid dominant
life cycle”?
3.
What type of gamete is produced by an antheridial head? By an archegonial head?
4.
How does the sporophyte generation of the moss acquire nutrients if it is not photosynthetic?
5.
What process is used by the fern sporophyte to produce spores? Are these spores diploid or haploid?
6.
Is the alternation of generations life cycle of the fern “sporophyte dominant” or gametophyte dominant”? Support your
answer.
7.
What features do you look for to classify a plant as vascular?
To Hand In
1. Labeled drawings of microscope slides and specimens
2. Answers to questions
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