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INVASION OF LAND
*dioecious
Gymnosperms…

[Cyclades*
Ginkogales*
Gnetales]
Coniferals 1)Pinaceae
2)Taxodiacea
3)Cupressaceae
4)Taxaceae

The height of a tree
monoecious*
having the anther (male) and carpels (female) in separate flowers on
same individual
...

• Ability of the organism to start growing on land required a whole range of
different adaptations
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• Sporophyte- diploid protected inside a gametophyte —> idea of Embryophyta
• Think about the various aspects of being able to transport water - stelar
Anatomy
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- ability to branch vascular strands [microphylls
and megaphylls]
• In ferns you start to see the megaphyll
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• Root and soil- invasion of land required soil- its biogenic and appeared with
the action of organisms
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Gymnosperms
• Cyclades- are dioecious in nature
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Term used to describe this is dioecious
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• Dioecious where the male and females are on separate individuals
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• Most plants are hermaphrodites
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Gnetales
• Important when thinking about the evolution of conifers
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Looks like an angiosperm rather than a conifer
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• hemitracheophytes in mosses refer to the relatively simple vascular system it
harbours
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[Winterdry] These organisms with needle like structures can survive desiccation
during the winter
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• Drugs present in conifers that are used for cancer therapies of various types
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• In a gymnosperm, what will happen in a diploid parent is you’ll get the
induction of a sporophyte inside a gametophyte
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Can get 4 haploid structures inside the
nucellus
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With the fern, the gametophyte has a separate multicellular form
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• Within the gymnosperms the fertilization event occurs in 2 different systems
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Motile sperm present inside the growth tube causes fertilization to occur
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Have the
outer integument which is part of the sporophyte which is diploid in
nature
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This then contains the diploid zygote
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This works effectively in terms of
protecting the new progeny in terms of invasion of land
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Height of a tree
• Sequoia- Really tall tree - 100 meters in height
• Question is how high can a tree actually grow? Associated with aspects of
flow of water inside the plant and the constraints of water transport as the
plant gets taller and taller
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Water is basically initially coming from the roots
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In
order for plants to grow to a great height, they have to have a complex
root system and hence a complex vascular system as well
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• In terms of thinking about the heights of trees, they normally stop at around
30m
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The maximum however is 100m in
terms of the ability of the organism to pull up water
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Absorption into the root from the soil, through the columns of
the xylem and in greater detail you see the ability of water to move
through them up through the stem and eventually to the leaves of the cell
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• Will then go into the stem or the trunk of the tree
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Have xylem
vessels like a long thread that extend up to the leaf in a very complex 3D
method
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• Want that interconnection because if a beaver or animal cuts through one of
those connections, the presence of others help the plant to survive and
therefore complexity of the eustele is important
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Have lots of cells that
contain chloroplasts
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Have xylems and water
flow as well
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Though the xylem into the tissues and eventually escaping into the
air
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Flow rates of water through
the stem is in the range of 2- 20 m/hr
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• Water leaves the stomates through evaporation
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Ability of that evaporation
to pull water through the xylem vessels- can measure that through
negative pressure measured in mega pascals
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The amount of pulling force required for a
plant that is 100m in height is 6mega pascals
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water is strong enough and has a tensile
strength that is strong enough except when it gets dry enough, water
strands will break

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