Biology 213
Name: _________________________
Lab 4a: Plants 1-Nontracheophytes
and Seedless Vascular Plants
Objectives:
 Identify the major structures of a moss.
 Describe the life cycle of a typical bryophyte; distinguish between the gametophyte and sporophyte
generations.
 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
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.
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 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.
1) Nonvascular plants (Mosses, Hornworts, and Liverworts)
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 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. We’ll use the
mosses as our representative sample today to try to visualize the complete lifecycle. As you examine
each slide, draw and label them in your lab notebook, and try to connect each stage to the lifecycle!
1A. The Mosses (Bryophyta)
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.)
Define and/or recognize: gametangia (antheridium, archegonium), sporangia (capsule), gametophyte,
sporophyte, “leaves”, protonema
Live specimens: Observe the various species of moss
Biology 213
2) Seedless vascular plants (the Ferns and their relatives)
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, vascular tissue, gametophyte, antheridia, sperm,
archegonia, and eggs
2A. Ferns
As above, draw each of the stages listed below in your lab notebook, labeling key structures and
connecting each stage to the lifecycle.
Slides: fern sporangia c.s., fern prothallus (antheridia and archegonia), fern prothallus (young
sporophyte)
Live or fresh specimens: fern sporophyte fronds
2B. Horsetails
Horesetails have a very similar lifecycle to their relatives, the ferns. We’ll be looking at either a crosssection (x.s.) or longitudinal section (l.s.) of the sporangia from the diploid sporophyte.
Slides: Equisetum strobilus, l.s. and x.s., Equisetum sterile stem tip x.s.
Live specimens (if available): Equisetum sporophyte plants
Postlab Questions to Answer:
1. Are the “leafy” (photosynthetic) portions of the moss the sporophyte or gametophyte generation? What
evidence would you use to support your answer?
2. What type of gamete is produced by an antheridial head? By an archegonial head? Provide a labeled
sketch from the notes in your lab notebook to illustrate what you expect to see in each of these structures.
3. How does the sporophyte generation of the moss acquire nutrients if it is not photosynthetic?
4. What process is used by the fern sporophyte to produce spores? Are these spores diploid or haploid?
5. Is the alternation of generations life cycle of the fern “sporophyte dominant” or “gametophyte dominant”?
Support your answer.
6. What features do you look for to classify a plant as vascular?
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