EKU General Botany Lab
Nonvascular Plants
There are three phyla of nonvascular plants, the Phylum Hepatophyta (liverworts), Phylum Anthocerophyta (hornworts), and Phylum Bryophyta (mosses). The plants of these phyla often are called nonvascular cryptogams, because they do not have pollen or seeds. Today, we’ll study only the Hepatophyta and Bryophyta.
PHYLUM HEPATOPHYTA (the liverworts)
As you study liverworts, you might want to refer often to the life cycle of a typical liverwort, on pp. 354-355 of your textbook. There also are some excellent pictures on pp. 348-353. Keep in mind that the gametophyte is the dominant phase of all liverwort life cycles.
Thallose Liverworts
Marchantia
LIVING GAMETOPHYTE
Examine the living gametophyte (sometimes called a thallus ) on display on the side counter under a dissecting microscope. Note the following structures: gametophyte thallus, air pores, rhizoids . Also examine any other living thallose liverworts that are available.
What is a thallus?
PRESERVED MATERIAL
On the side counter, examine preserved antheriophores and archegoniophores under the dissecting scope provided. Note the following: archegonial rays, antheridial disk . Note that all the structures you see are haploid.
PERMANENT SLIDES
Examine the following permanent slides:
Cross section of gametophyte (slides in separate slide box, on side counter)
Note air pores, photosynthetic tissue [look for chloroplasts in cells, upper part of thallus], nonphotosynthetic tissue, rhizoids with internal pegs, scales .
What functions do air pores, rhizoids, scales and pegs perform?
Cross section, gemma cup -- on display
under compound microscope, side
counter)
(the slide label may say "cupule" = an archaic term for gemma
cup)
What are gemma cups?
What are gemmae ?
What is their function?
How do they carry out their function?
How else do liverwort gametophytes reproduce asexually?
Marchantia antheridia (slide #1, slide box C)
Note antheridiophore, antheridial disk, antheridia, sperm, rhizoids . Note that all structures are haploid.
? What are the functions of all structures?
Marchantia archegonia (slide #2, slide box C)
Note archegoniophore, archegonial rays, archegonium (neck, venter, egg), rhizoids . Note that all structures are haploid.
Marchantia sporophyte (slide #3, slide box C)
In addition to the structures noted above, note the sporophyte (foot, seta, sporangium), spores, elaters, calyptra.
What are the functions of all structures?
Which structures are haploid and which structures are diploid?
What are the functions of all structures?
Do you see any rhizoids?
Leafy Liverworts
(see Fig. 16-16, p. 356, textbook)
There are many more species of leafy liverworts than of thalloid liverworts. The gametophytes of leafy liverworts look like mosses, except that their leaves are arranged in two parallel rows, and there are small additional leaflike structures (called amphigastria) underneath the main leaves. Leafy liverworts are common on tree bark, rocks and especially in wet places, such as on rocks near waterfalls.
Frullania
LIVING GAMETOPHYE
These gametophytes were collected from trees in a yard near Richmond. Be sure to examine them carefully under the dissecting scope on the side counter. Note the overlapping leaves. Leafy liverworts are common, but people hardly ever see them.
[THE FOLLOWING MAY BE OBSERVED, ESPECIALLY IN FALL SEASON.]
These gametophytes have sporophytes on them, and may be shedding spores. Very few people ever see liverworts shedding spores.
Which structures are haploid and which ones are diploid?
What is the function of the spores?
How do you think the spores are
spread from place to place?
[Two bonus points--added to the
midterm lab exam--for the first three people who guess correctly what kind
of tree the Frullania was growing on. Only one guess per person,
and you must e-mail your guess to the instructor before the next lab
period.]
PHYLUM BRYOPHYTA (the mosses)
Moss gametophytes usually have small leaves that do not overlap like those of leafy liverworts. When moss spores germinate, they form filamentous structures called protonemata. After a time of growth, the protonemal filaments form multicellular budlike structures that grow into mature, leafy moss gametophytes. Refer often to the moss life cycle diagram on pp. 362-363 of your textbook, and to pictures on pp. 358-366.
LIVING MOSS PROTONEMATA
Make a temporary water mount from the protonema culture. Note: protonema cells, chloroplasts, rhizoids.
How can you distinguish moss protonemata from algae?
Are chloroplasts present in the rhizoids?
PERMANENT SLIDE, MOSS PROTONEMATA
Note: protonemata, and “buds .”
Are any rhizoids visible?
LIVING MOSS GAMETOPHYTES AND SPOROPHYTES
If these are available, examine them under the dissecting scope provided on the side counter. Pay special attention to the sporophytes, noting the capsule and seta .
Do any of the sporophytes have a calyptra ?
What is the calyptra, what does it do, and is it haploid or diploid?
Can you find an operculum ? Is is haploid or diploid?
Are
any peristome teeth
visible?
For
all structures -- are they n or 2n?
PERMANENT SLIDES OF MOSS GAMETANGIA
Mnium antheridia (slide #8, slide box C)
Note antheridia, and sperm .
Note that all structures are haploid.
Mnium archegonia (slide #9, slide box C)
Notice that these archegonia are erect, not pendulous [hanging down] as in Marchantia. Note archegonium, archegoniophore, neck, venter, egg .
Polytrichum capsule (slides 10 and 11, slide box C)
The capsule is the meiosporangium of mosses. Note spores, columella, tapetum, operculum, and peristome region . (The common name of Polytrichum is hairycap moss.)
Which structures are haploid and which structures are diploid?
What the the function of each structure?
The Spanish Moss on display is not a moss. It is a vascular plant that reproduces by flowers, fruits and seeds. It is related to pineapple! (Pineapples, Spanish moss, and their relatives are called bromeliads.) Sometimes bromeliads are called air plants -- and what does that mean? Also, many bromeliads are epiphytes -- and what does that mean?