Introducing Bryophytes

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Introducing Bryophytes

• Basic Biology

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What is a Bryophyte?

• Bryophytes are common plants that are easily
  found wherever you are.

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What is a Bryophyte?

• First, they are green plantsthey produce their
  own food with photosynthesis.

They take water and carbon dioxide and use the
energy in sunlight to produce sugar and oxygen.
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What separates Bryophytes from other land plants?

• Most of the flowers and trees you see around you
  have roots, stems and leaves. The roots absorb
  water and nutrients from the soil which are then
  distributed throughout the plant in a network of
  tiny tubes. These tubes are waterproofed by a
  complex sugar called lignin.

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What separates Bryophytes from other land plants?

• Bryophytes do not have roots, or this system of
  tubes lined with lignin. They have to absorb
  their water and nutrients directly from the
  surface they grow on, or from the air.
• This means that most of the plant has to be very
  thin to allow all of the plant to be exposed to
  these resources.

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Bryophytes

• The lack of this "plumbing system" also means
  that bryophytes can't grow very tall. The tallest
  bryophyte grows to nearly 1 meter tall, but most
  are smaller than a few centimeters .

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What else separates Bryophytes from other land
plants?

• Inside the cells of all of the ferns, flowers and
  trees on earth, there are two sets of chromosomes
  (2N or diploid). Chromosomes are long strands of
  DNA that carry the genes that tell the plant how
  to grow. In people, who also have two sets of
  chromosomes, one set comes from the mother, and
  one from the father. Plants are similar, so one
  set comes from a male plant (or a male portion of
  the plant), and one set comes from the female
  plant (or a female part of the plant). But, as
  you can see, there has to be at least a short
  part of a plant's life cycle where the pair of
  chromosomes split up so that the males or females
  can contribute their half to the offspring. This
  portion of the life cycle is called the haploid
  or 1N phase. So the life cycle of all plants
  makes a circle with some portion of it with one
  set of chromosomes-- the haploid or gametophyte
  phase, and some portion of it with both sets of
  chromosomes--the diploid or sporophyte phase.

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Life cycle of a Fern
Notice that the fern frond, the part that you
think of when you think of a fern, is above the
line in the diploid (2N) phase. Most people have
never seen the haploid phase of a fern, which is
about the size of a dime, and only survives for a
short period
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Life cycle of a Bryophyte
Notice on this chart that the part you think of
as a moss is below the line and in the haploid
phase. Here the diploid sporophyte is dependant
on the haploid gametophyte, which is the exact
opposite of the ferns and other land plants.
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Diploid (2N) Dominant
zygote
(2N)
(1N)
green algae
bryophytes
ferns
gymnosperms
Haploid (1N) Dominant
angiosperms
DECREASING SIZE OF GAMETOPHYTE PHASE
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What is a Bryophyte?

• Generally proscribed as 3 major groups

MOSSES About 10,000 species worldwide
LIVERWORTS About 7,000 species worldwide
HORNWORTS About 150 species worldwide
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What does a moss look like?

• Moss gametophytes (1N) are organized as leaves
  on a stem

Most are simple and unbranched and are called
ACROCARPS
Others are highly branched and are called
PLEUROCARPS
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What does a moss look like?

• The sporophyte (2N) phase is a capsule on a stalk
  growing on the gametophyte (1N)

Sporophyte
Gametophyte
Mouth of the capsule after the lid falls off
The capsules come in many different shapes
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What does a Liverwort look like?

• There are 3 general forms
• The first is the Complex Thalloid form

If you cut through one of those pores with a very
sharp blade, and looked at it through a
microscope, this is what it would look like.
Pore into air chamber
Photosynthetic filaments
Each one of the little white dots on this thallus
is a pore into the air chamber
The gametophytes body is called the Thallus and
is differentiated into air chambers with
photosynthetic filaments at the bottom
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What does a Liverwort look like?

• Three general forms
• Complex Thalloid form

The sporophyte in the complex thalloid form is
either elevated on a stalk growing from the
thallus, or embedded in the thallus
Sporophyte
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What does a Liverwort look like?

• Three general forms
• The second is the Leafy form

The sporophyte breaks open into 4 sections
releasing the spores and these spiral banded
bodies called elaters
The Sporophyte is a club like capsule on a watery
stalk called a seta that grows from the
gametophyte
The Gametophyte
is a stem with leaves like a moss
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What does a Liverwort look like?

• Three general forms
• The third is the Simple thalloid form

The sporophyte in the simple thalloid form is
very similar to the leafy forma club-like ball
atop a watery stalk growing on the thallus.
The gametophytes body is called a Thallus which
is relatively homogenous--without air chambers
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What do Hornworts look like?

• The Gametophyte (1N) body is called a thallus and
  has a gummy bear texture

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What do Hornworts look like?

• The sporophytes (2N) are needle-like horns that
  grow out of the gametophyte. They split from the
  end downward, releasing the spores.

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Bryophyte Ecology

• Where do bryophytes grow?
• Most people think that bryophytes grow only in
  moist, shaded places.
• WRONG! Different species of bryophytes can grow
  in different places, and on different surfaces.
  They can grow on dry rocks, tree bark, on
  buildings, on dirt, and even under water. Keep
  clicking to see examples of all these habitats.

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Where do bryophytes grow?
Fontinalis in a flowing stream
Orthotrichum on dry rock
Dendroalsia on tree bark
Asterella on soil
Tortula on brick mortar
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Bryophyte Ecology

• But wait many of those surfaces often dry out
  completely
• If a plant has no roots that can penetrate to
  some wetter place, how can it survive?
• The bryophytes that grow in these dryer places
  have evolved to store chemicals in their cells
  that can be used to rebuild the cells once water
  is available again. This is called dessication
  tolerance

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Bryophyte Ecology
Here is a photo of a moss growing on a dry rock.
The left hand side has had water poured on it.
Within minutes, the left hand side has begun
repairing its cells, and even started
photosynthesis!