A Look at the Plant Kingdom Lab 8- Bio 160

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Lab 8- Bio 160

A Look at the Plant Kingdom

OBJECTIVES

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

2)

3) would you use to support your answer?

What type of gamete is produced by an antheridial head? By an archegonial head?

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, 1 st

4 nucleate embryo sac. (ovule, megasporangium)

2)

Live or fresh specimens:

various samples of flowers o

Draw and locate the following structures from two of the flowers: sepals, petals, stamens, filaments, o anthers, pollen grains, carpels, stigmas, styles, ovaries.

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.

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

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