Hornworts

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Hornworts

• Domain Eukarya
• Kingdom Plantae
• Phylum Bryophyta

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Anthoceros gametophyte thallus with elongating
sporophyte Why is this called a hornwort?
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Anthoceros - the hornwort
The gametophyte is much like a thallose
liverwort. The sporophyte is the horn of the
hornwort.
Gametophyte
http//botit.botany.wisc.edu/images/130/Bryophytes
/Anthocerophyta/Anthoceros.jpg
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Hornwort Thallus Cross Section
photosynthetic upper epidermis
cortex
lower epidermis
rhizoids
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Compared to the liverwort thallus, what is
missing?
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Cyanobacteria are often symbionts!
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What cellular details can you find?
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The Anthoceros gametophyte thallus has one
chloroplast per cell...
Obviously like all other bryophtyes chlorophylls
a and b xanthophylls and carotenoids
http//botit.botany.wisc.edu/images/130/Bryophytes
/Anthocerophyta/Pyrenoids_MC.low.jpg
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Compared to the liverwort, what is different
about the location of the antheridia in hornworts?
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This Anthoceros gametophyte
shows three antheridia
http//www.dipbot.unict.it/sistematica_es/Immagini
/18002.JPG
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Here is the best I could find on the web to show
the archegonium which is embedded in the hornwort
gametophyte thallus.
http//www.science.siu.edu/landplants/Anthocerophy
ta/images/Phaeoc.laevis.arch.JPEG
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The artist would lose one point abovewhy? What
are some missing items as well?
The spore mother cell is better known as
sporocyte! We shall find out why this is so, as
we proceed to more-derived plants.
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Hornwort sporophyte (with attached gametophyte)
gametophyte collar
foot
intercalary meristem
stalk
sporangium
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Whole mount closeup
What apomorphy is featured here?
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Longitudinal section
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The Anthoceros sporophyte foot is embedded in the
gametophyte. The sporophyte seta has an
intercalary meristem.
Gametophyte Thallus
Intercalary Meristem
Foot
Gametophyte rhizoids
http//botit.botany.wisc.edu/images/130/Bryophytes
/Anthocerophyta/Sporophyte_foot_MC.jpg
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The Anthoceros sporophyte has evolved guard cells
and stomata.
While initially dependent on the gametophyte, it
carries out its own photosynthesis. The
sporophyte may continue to grow while the
gametophyte degenerates.
Two apo-morphies are shown here which?
http//botit.botany.wisc.edu/images/130/Bryophytes
/Anthocerophyta/stomata.jpg
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What is this? How could it be labeled?
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The Anthoceros sporangium is linear and
indeterminate in size. It is surrounded by a
layer of cortex and epidermis.
The sporocytes divide by meiosis, producing
meiospores. The tri-radiate marks and surfaces
that the tetrad of spores impress upon each other
are shown here.
http//www.biology.lsa.umich.edu/courses/bio255/an
tho2.jpg
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Hornwort sporangium ls
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cs, ls, or wm?
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What would be the labels on this?
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Here is the cross section of a maturing part of
the hornthe Anthoceros sporophyte.
In the center of the sporophyte, you can find the
hydroids and leptoids!
http//www.biology.lsa.umich.edu/courses/bio255/an
tho.jpg
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The sporophyte maturing to shed spores to the wind
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The Anthoceros sporophyte matures from tip to
base shedding almost unlimited spores due to
intercalary meristem at base.
http//botit.botany.wisc.edu/images/130/Bryophytes
/Anthocerophyta/Sporophytes_lg_DH_.jpg
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The tip of the Anthoceros sporophyte matures
first, shedding the spores to the wind.
http//www.hiddenforest.co.nz/bryophytes/hornworts
/anthocertaceae/images/horn03.jpg
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The Life Cycle of Anthoceros