Download Lab 7 Plant Kingdom

Lab 8- Bio 160
A Look at the Plant Kingdom
OBJECTIVES
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To examine examples of plants (moss, ferns, conifers and flowering plants)
To recognize the sexual structures of both moss, fern, conifer and flowering plants
To examine examples of organisms that live the “alternation of generations” life cycle
To hypothesize about the pollinators of a flower using the structures and positioning of the floral structures
General Introduction:
Plants are generally defined as multicellular, photosynthetic eukaryotes. Plants cells have cell walls composed of
cellulose, and store carbohydrates as starch. They utilize two photosystems in photosynthesis with two forms of
chlorophyll (a and b).This list of characteristics is not unique to the Plant Kingdom however, as several phyla of algae
(Kingdom Protista) also fit the description.
Therefore, the definition of plants is refined 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.
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 or gametes 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).
Using lecture and your book, we will examine the Plant Kingdom through a series of 4 evolutionary stages. The
nontracheophytes (mosses) 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
Gymnosperms, and the evolution of flowers is studied in the Angiosperms. In lab activities we will focus on the mosses,
ferns, conifers and flowering plants.
Note: Some of these slides are difficult to interpret. Do your best and ask me if you have questions.
PROCEDURE
Part A: The Bryophytes (mosses)
Background: The nonvascular plants represent a group of plants from before true vascular plants evolved.
Materials are transported through the plant body, but the specialized water and food conducting vascular cells of
“modern” plants. Consequently, nonvascular plants are generally low-lying, mat-like plants in which water is
absorbed both through the “leaf-like” structures as 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 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”, rhizoids
Slides: Mnium or moss archegonial head (l.s.), Mnium or moss antheridial head (l.s.), Mnium or Moss capsule
Live specimens: Observe the various species (and life cycles) of moss
Lab 2 Cells
Questions for review (answer these on a separate sheet of paper.)
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) What type of gamete is produced by an antheridial head? By an archegonial head?
3) How does the sporophyte generation of the moss acquire nutrients if it is not photosynthetic?
To Hand In
1. Labeled drawings of microscope slides and specimens
2. Answers to questions
1) 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)
Live specimens: fern sporophyte fronds
Horsetails
Live specimens: Equisetum sporophyte plants
Questions for review
1) What process is used by the fern sporophyte to produce spores? Are these spores diploid or haploid?
2) Is the alternation of generations life cycle of the fern “sporophyte dominant” or gametophyte dominant”? Support
your answer.
To Hand In
3. Labeled drawings of microscope slides and specimens
Lab 2 Cells
2) Part B: The Seed Plants: Phylum Coniferophyta (The Conifers)
Background: The Phylum Coniferophyta represents a larger group of organisms known as gymnosperms. The
gymnosperms bear naked seeds on sporophylls. The conifers are the largest of 4 phyla within this group. The
conifers (“cone-bearing plants”) are represented in lab by several species found on campus (pines, cedars, etc.)
and by prepared slides.
Almost all the conifers are “evergreen” holding their needle-like or scale-like leaves year round. This
allows for growth year round, although this growth is reduced in the seasons of less sunlight. The reduced leaves
are adapted to colder, drier climates with a thick cuticle, and stomata located in pits. Commercially, most of our
lumber and paper pulp comes from the wood of conifers.
We will examine the pine tree structures in lab, and will focus on the life cycle stages discussed above.
The diploid pine sporophyte (the tree) contains two types of cones. Staminate (or pollen) cones contain the
microsporangia that give rise to the microgametophytes, pollen grains, containing the sperm nuclei. Ovulate
cones contain the megasporangia that give rise to the megagametophytes, ovules, containing the egg nuclei.
Define and/or recognize: see structures listed below
Slides:
Pinus, ovulate cone, l.s. Observe megasporophyll, ovule
Live specimens: Branches and cones (staminate and ovulate) from a conifer
The Angiosperms (flowering plants)
Background: The Angiosperms are recognized as the “flowering plants”. The term angiosperm more correctly
refers to all plants that have fruiting structures.
A flower is a stem tip with up to four whorls of modified leaves. The outermost whorl is composed of the
sepals. Sepals are usually green and enclose and protect the flower before it opens. Sepals may be attractant
colors other than green, as in the lily that we will examine in lab.
The next inner whorl contains the petals. Petals are generally attractant colors (advertisements for
pollinators) and along with the sepals are sterile structures in the flower.
The next inner whorl of a flower is the stamen. These are essentially the “male” parts of the flower. A
stamen is made up of an anther and filament. The filament positions the anther appropriately for the incoming
pollinator, as the anther contains the pollen producing structures. The anther contains, the pollen grain.
The innermost whorl of the flower are the carpels. A carpel is made up of three parts: a stigma, style and
ovary. The stigma is the sticky end of the carpel that receives pollen. The style is the tube that connects the
stigma to the ovary, and also positions the stigma to best receive the pollen. The ovary contains the “female”
reproductive structures. The ovary contains the ovary chamber and the ovule (containing the egg cell). The ovule
matures later into the seed.
Upon fertilization, the pollen grain produces a tube that grows through the style to an ovule in the ovary.
Two sperm nuclei are delivered to the ovule for a unique double fertilization. One sperm nucleus fertilizes the
egg nucleus to become the diploid zygote, and the second sperm nucleus fertilizes the two polar nuclei of the
ovule becoming the triploid endosperm. The zygote will develop into the new sporophyte, and the triploid
endosperm is the nutritive material of the seed.
In angiosperms, a fruit develops around the seed(s). The fruit is essentially a mature ovary. After
fertilization, the ovary matures, ripens, and becomes the fruiting structure. Basically, the fruit assists in dispersal
of the seed(s). Some fruits are shaped like wings for wind dispersal, some burrs that cling to animal fur, and some
are edible relying on animals to consume the fruit and pass the seed(s) when they excrete their wastes.
Lab 2 Cells
Define and/or Recognize: see structures listed below
Slides:
Lilium: Anthers, pollen tetrads. (microsporangium)
Pollen grains. (haploid nuclei)
Lilium: Ovary, 1st 4 nucleate embryo sac. (ovule, megasporangium)
Live or fresh specimens: various samples of flowers
o Draw and locate the following structures from two of the flowers: sepals, petals, stamens, filaments,
anthers, pollen grains, carpels, stigmas, styles, ovaries.
o In addition, hypothesize about the pollinators that may visit these flowers.
Questions for review
1) Define the following terms: complete flower, incomplete flower, perfect flower, imperfect flower.
2) How did the shape and positioning of the floral structures give you clues about the pollinators of the flower?
3) How do flowering plants and pollinators demonstrate co-evolution?
To Hand In
1. Labeled drawings of microscope slides and specimens