Life Cycle of Nonvascular
Plants
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
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Printed: November 8, 2015
AUTHORS
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Life Cycle of Nonvascular Plants
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Life Cycle of Nonvascular
Plants
• Outline the life cycle of nonvascular plants.
• Distinguish between antheridia and archegonia.
Haploid or diploid. Which would you say is dominant?
That may depend on the plant. Start with moss. The typical nonvascular plant. But such a simple plant has a very
interesting life cycle. Whereas most kinds of plants have two sets of chromosomes in their vegetative cells, mosses
have only a single set of chromosomes. So, how does meiosis occur?
Life Cycle of Nonvascular Plants
Nonvascular plants include mosses, liverworts, and hornworts. They are the only plants with a life cycle in which the
gametophyte generation is dominant. Figure 1.1 shows the life cycle of moss. The familiar, green, photosynthetic
moss plants are gametophytes. The sporophyte generation is very small and dependent on the gametophyte plant.
The gametophytes of nonvascular plants have distinct male or female reproductive organs (see Figure 1.2). Male
reproductive organs, called antheridia (singular, antheridium), produce motile sperm with two flagella. Female
reproductive organs, called archegonia (singular, archegonium), produce eggs.
In order for fertilization to occur, sperm must swim in a drop of water from an antheridium to an egg in an archegonium. If fertilization takes place, it results in a zygote that develops into a tiny sporophyte on the parent gametophyte
plant. The sporophyte produces haploid spores, and these develop into the next generation of gametophyte plants.
Then the cycle repeats.
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FIGURE 1.1
Like other bryophytes, moss plants spend
most of their life cycle as gametophytes.
Find the sporophyte in the diagram. Do
you see how it is growing on the gametophyte plant?
FIGURE 1.2
The reproductive organs of bryophytes
like this liverwort are male antheridia and
female archegonia.
Summary
• In nonvascular plants, the gametophyte generation is dominant. The tiny sporophyte grows on the gametophyte
plant.
Explore More
Use this resource to answer the questions that follow.
• Life Cycle of a Nonvascular Plant at http://www.gardenguides.com/130899-life-cycle-nonvascular-plant.
html .
1. Distinguish between gametophytes and sporophytes of nonvascular plants.
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Chapter 1. Life Cycle of Nonvascular Plants
2. Describe alternation of generations in a nonvascular plant.
3. What are the antheridium and archegonium?
4. Describe sperm cells of a nonvascular plant.
Review
1. Describe antheridia and archegonia and their functions.
2. Create your own cycle diagram to represent the moss life cycle.
References
1. Mariana Ruiz Villarreal (LadyofHats) for CK-12 Foundation. Moss life cycle . CC BY-NC 3.0
2. Liverwort: User:Lamiot/Wikimedia Commons; Archegonia and Antheridia: Hermann Schachner. Reproduc
tive organs of bryophytes . Liverwort: CC BY 3.0; Archegonia and Antheridia: Public Domain
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