Nonvascular Plants
Jessica Harwood
Douglas Wilkin, Ph.D.
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AUTHORS
Jessica Harwood
Douglas Wilkin, Ph.D.
EDITOR
Douglas Wilkin, Ph.D.
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Printed: January 14, 2015
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Niamh Gray-Wilson
Jean Brainard, Ph.D.
Sarah Johnson
Jane Willan
Corliss Karasov
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C HAPTER
Chapter 1. Nonvascular Plants
1
Nonvascular Plants
• Define bryophyte.
• Describe examples of nonvascular seedless plants.
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What did forests look like millions of years ago?
The trees you see today did not exist. Nonvascular plants and vascular seedless plants first dominated the forest. The
remains of these forests formed the coal that we depend on today.
Nonvascular Seedless Plants
Nonvascular seedless plants, as their name implies, lack vascular tissue. Vascular tissue is specialized tissue that
transports water, nutrients, and food in plants. As they lack vascular tissue, they also do not have true roots, stems,
or leaves. Nonvascular plants do often have a “leafy” appearance, though, and they can have stem-like and root-like
structures. These plants are very short because they cannot move nutrients and water up a stem.
Nonvascular seedless plants, also known as bryophytes, are classified into three phyla:
1. Mosses
2. Hornworts
3. Liverworts
Mosses
Mosses are most often recognized as the green “fuzz” on damp rocks and trees in a forest. If you look closely, you
will see that most mosses have tiny stem-like and leaf-like structures. This is the gametophyte stage. Remember that
a gametophyte is haploid, having only one set of chromosomes. The gametophyte produces the gametes that, after
fertilization, develop into the diploid sporophyte with two sets of chromosomes. The sporophyte forms a capsule,
called the sporangium, which releases spores ( Figure 1.1).
FIGURE 1.1
Sporophytes sprout up on stalks from this bed of moss gametophytes.
Notice that both the sporophytes and gametophytes exist at the same
time.
Hornworts
Hornworts are named for their appearance. The "horn" part of the name comes from their hornlike sporophytes,
and “wort” comes from the Anglo-Saxon word for herb. The hornlike sporophytes grow from a base of flattened
lobes, which are the gametophytes ( Figure 1.2). They usually grow in moist and humid areas.
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Chapter 1. Nonvascular Plants
FIGURE 1.2
In hornworts, the “horns” are the sporophytes that rise up from the leaflike gametophyte.
Liverworts
Liverworts have two distinct appearances: they can either be leafy like mosses or flattened and ribbon-like. Liverworts get their name from the type with the flattened bodies, which can resemble a liver ( Figure 1.3). Liverworts
can often be found along stream beds.
FIGURE 1.3
Liverworts with a flattened, ribbon-like body are called thallose liverworts.
Summary
• Nonvascular plants lack seeds and vascular tissue.
• Nonvascular plants include the mosses, the hornworts, and the liverworts.
Explore More
Use the resource below to answer the questions that follow.
• Nonvascular Plants at http://www.youtube.com/watch?v=kBPLKUTtXBM (3:22)
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MEDIA
Click image to the left or use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/57441
1.
2.
3.
4.
5.
How do bryophytes keep their eggs from drying out?
How does bryophyte sperm locate the bryophyte egg?
What happens in the archegonia?
What happens in the antheridium?
Where does fertilization of the bryophyte egg occur?
Review
1. What is a bryophyte?
2. What are examples of nonvascular plants?
3. Why do nonvascular plants tend to be very short?
References
1. takomabibelot. Sporophytes sprout up on stalks from this bed of moss gametophytes . CC BY 2.0
2. Jason Hollinger. In hornworts, the horns are the sporophytes that rise up from the leaflike gametophyte . CC
BY 2.0
3. Jason Hollinger. Liverworts with a flattened, ribbon-like body are called thallose liverworts . CC BY 2.0
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