Lab Topic 16
Investigating Plant Phylogeny: Seedless Plants

 

Bryophyta

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How to study for the practical

Learn the language:
For this topic a vocabulary list is given in your lab manual. You need to know the definitions of the terms. Make flashcards for those that you do not know and work to learn the definitions.

Seek the big picture:
In lab manual a list of Key Concepts and Objectives are given. Be sure that you can explain how the lab addresses or illustrates each.
You will probably find it helpful to outline the background section at the beginning of each lab topic in the manual as it attempts to give you a “big picture” overview.

Apply your knowledge of terms and concepts to reality:
Review the images on this www site for each lab topic in the practical.

You need to develop visual memory so that you can recognize images similar to these in the lab practical questions.

As you look at the images, answer any questions that given with the image. Use you lab notebook and lab manual to check your answers.

Synthesize and consolidate you knowledge:
Draw life cycle diagrams where you can. For each organism, know when mitosis and meiosis occur in the life cycle. Be able to describe the ploidy levels as well as the names of different life cycle stages. If there are special organs involved in sexual or asexual reproduction, know the names, functions and what they look like.

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Pterophytes (ferns) and Related Seedless Vascular Plants

Sporophyte stages of seedless vascular plants (Tracheophytes)

Equisetum (Horse tail)	Close up of stem of Equisetum

Psilotum (Whisk fern)	Lycopodium (Club mosses)

• What characteristics do these plants have in common?
• What phyla do these different plants belong to?
• Can these plants best be described as sporophyte dominant or gametophyte dominant?
• Overall, ferns are larger and more diverse than mosses mainly because
• (A) ferns can absorb water and nutrients more effectively;
• (B) ferns have vascular transport system;
• (C) ferns produice seeds which allow them to grow faster;
• (D) mosses are less sensitive to water stress.
• Name the two stages in the alternation of generations these plants exhibit. Which stages are haploid and which diploid?
• Is this stage in the life cycle the result of asexual or sexual reproduction?
• How are these plants better adapted to survival in a terrestrial environmetn than are mosses?

	Cross section of a Psilotum stem (stained) Name one function of the vascular tissue found in these plants. What kind of tissues does this organism have that mosses and liverworts do not?  Many different types of plants are called tracheophytes. What do they all have in common?
	Cross section of a fern stem (stained) THis specimen is not studied in lab but is included here for comparison purposes. Note the vascule bundle in the center of the cross section of the stem with large heavy walled xylem cells.

Phylum Pterophyta,

Ferns, whisk ferns and horesetails

Gametophyte Stages

A gametophyte stage of a fern with rhizoids.  What is the ploidy level of this organism? What type of nuclear division leads to gamete production by this plant? What is the function of the rhizoids? What stage in the alternation of generation found in fern is this? What is the function of this stage of the life cycle?

 

Stained gametophyte showing antheridia at  at 100X and  400X	Sperm
What is the function of the antheridium? Do cells in the antheridium divide by mitosis or meiosis to produce sperm?	What is the ploidy level of sperm? How do sperm get from the antheridium to the egg?

 

Stained gametophyte with archegonia at 35X	Stained gametophyte with archegonia at 100X	Sperm's eye view of archegonia showing canal into chambers holding eggs.
From what cell did the gametophyte originate? What is the ploidy level of this organism?	What do the archegonia contain?  Do cells in the archegonia divide by mitosis or meiosis to produce eggs? What type of nuclear division leads to gamete production by this plant?	How do the sperm reach the eggs to fertilize them? Based on the mode of fertilization, would you say that ferns are completely adapted to a terrestiral environment? Support your answer with reasons.

 

Stained sporophyte growing from gametophyte  Indicate which cells in this photo would be haploid and which diploid. What happens to the gametophyte stage as the sporophyte stage matures? The upright stalked structure originated from what cell in the basal structure?

Sporophyte Stages

Different species have different numbers of sori on under surface of frond. Others will produce sori on a separate stem.

 

Stained fern sori at 35X	Stained fern sori at 100 X
What is the name of structures inside the sori? What do these structures produce?  What type of nuclear division gives rise  to spores inside of these structures?	Are all spores produced in a sporangium identical? Why do you say so?

 

Stained fern sporangium with loose spores  Compare and contrast a spore and a seed. What type of nuclear division produces spores inside of these structures? Does fertilization occur inside these structures? What is the function of this structure? The spores in fern sporangia are (A) haploid; (B) diploid; (C) triploid How is the structure atop the sporangium (seen here) involved in the fern life cycle? What is the ploidy level of spores?

Fiddlehead  and mature fronds (Young sporophyte) What is the function of this stage in the life cycle of the fern? What is the ploidy level of the cells in the leaves in this stage of the fern life cycle? How is this plant adapted to a terrestiral environment? In this organism, are the gametophyte and sporophyte nutritionally independent? Can you give examples of plants where this not the case? Which of the following best describe the organism? A. Nonvascular, seed plant; B. Nonvascular, seedless plant; C. Vascular, seedless plant; D. Vascular, seed plant

General and  Comparative and  Questions

1. Describe how mosses and ferns show increasing adaptation to terrestrial environments when compared to colonial algae.
2. List four adaptations of plants to living on land.
3. What are the two  generations of the plant life cycle called and what are their ploidy levels?
4. Which of the following Divisions produce seeds:  Byophyta, Sphenophyta, Coniferophyta, Hepatophyta, Pterophyta, Lycophyta, Anthophyta?
5. If a fern spore contain 30 chromosomes, how many chromosomes woud you expect to find in an egg of a fern?
6. A student wanted to study stages of meiosis in ferns. He kept making microscope slides of antheridia and archegonia but never saw any cells in meiosis even though the ferns produced egg and sperm and were able to reproduce. Why was he not able to find meiotic stages?
7. Do you think that germinating spores or germinating seeds would be more susceptible to ultra-violet induced mutations? Why?
8. If you compared a cross section of a fern stem to that of moss stem, what differences would you expect to find?
9. Where would you expect to find the gametangia in a fern?
10. Why are ferns usually larger in size than mosses and liverworts?
11. Describe the role of water in fertilization in the ferns.
12. A high school biology class decided to grow ferns for the high school graduation. They knew that the sporophyte stage was the "showy" stage in the life cycle. They reasoned that all that had to do was plant spores and that they would germinate to give them sporophytes. Why is the project doomed?
13. How is the life cycle of a liverwort similar to that of a fern? How is it different?
14. Why would you not expect to find mosses and ferns living in a desert?
15. Is it possible to have male and female sporophytes? Gametophytes?
16. How does the location of the antheridium and archegonium in ferns differ from that in mosses and liverworts and why is this difference important?
17. List one major similarity and one difference between nonvascular and vascular plants other than vascular plants have vascular tissues.
18. Briefly discuss how seedless plants have adapted to a terrestrial environment.
19. In the tropics, some ferns are trees, reaching heights of 5 or more meters. What anatomical adaptation not found in mosses allows them to grow this tall?
20. Describe alternation of generations in a seedless plant lifecycle.  Specifically mention: the names and ploidy of the generations, what cell types they are produced from, and what types of cell division they use to produce the next generation.

American Bryology and Lichenology Society
American Fern Society
Great photo essay describing life cycle of royal fern, Osmunda

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Credits
Photos by Maria Oehler, Warren Dolphin, Youyou Moon and Botanical Society of America
Layout and text by W. D. Dolphin