Transcript PLANT DIVISIONS

PLANT DIVISIONS
Plants
• NOTE: We use the
term Divisions
instead of the term
Phyla when referring
to plants.
• Characteristics of
plant kingdom
members
– Alternation of
generations with the
diploid sporophyte
generation dominant
except in bryophytes
Evolution of plants from green
algae
• A certain group of green algae known as the
charophytes have the following in common with plants.
– Chloroplasts of both have thylakoids stacked as grana and
chlorophyll b and carotene to act as accessory pigments for
chlorophyll a.
– The % of cellulose in both is around 25%
– Similar mitosis and cytokinesis mechanisms
– Similar sperm structure for sperm
– DNA evidence backs this up.
– Body of some charophytes is haploid, but fertilized egg is
retained in the organism and grows and then does meiosis:
clue to how alternation of generations started.
Vascular tissue
– Most division (all
except bryophytes)
have vascular tissue of
xylem (water and
minerals) and phloem
(nutrients).
– Picture shows
vascular tissue in a
leaf in a bundle known
as a vein. These are
the lines you can see
in the leaf.
Carbon dioxide
• Plants lowered the levels of carbon dioxide from 25X
current levels to current levels over a period of 100 million
years as they adapted to and spread on land.
Invasion of land
• Stomata
• Cuticle
• Lignin: bonds to cell wall
cellulose to add strength and
waterproofing
• Vascular tissue: xylem and
phloem
• Roots: absorb nutrients and
water vs. rhizoids of moss and
holdfasts of algae that don’t.
• Seeds: dormancy
• Fruit: spreading seeds
• Flowers: cross pollination
Cuticle
– A waxy cuticle covers parts exposed to air to prevent
dessication. Openings in the cuticle (stomata) allow for
gas exchange and are controlled by the guard cells.
Guard cells
Cuticle, Dermal tissue, ground
tissue, and vascular tissue
Flagellated sperm vs. pollen
• The more primitive plants have flagellated sperm
that allow them to swim to the egg. This means
that the mosses, ferns, and other primitive plants
require water to have fertilization.
Fern sperm
Types of
pollen
Plant Divisions: Bryophyta
• MOSSES
• Dominant gametophtye
generation (green)
• Also includes liverworts and
hornworts
• Need sperm to fertilize egg
• NO vascular tissue limits
height of the plant and
therefore have no true roots,
stems, or leaves.
• haploid spores are made by
meiosis in the sporangium of
the sporophyte.
Moss
sporophyte
Other Bryophytes
Hornwort
Liverworts
Gametophytes
• Antheridium
• Male gametophyte
• Makes sperm
Archegonium
Female gametophyte
makes egg
Lycophyta: club mosses,lycopods
They have vascular tissue.
Inconspicuous gametophyte can live underground
for ten years.
• Lycopodium
Club mosses
Sphenophyta: horsetails
Once occupied the niche of trees before conifers and
flowering plants existed
• They are homosporous
Pterophyta
• Homosporous: create one spore that is
bisexual.
• Vascular tissue but no seeds: allows them
to get taller, but limits them to shady moist
areas for reproduction.
• Fronds: big “leaf like” arrangement
• Fiddlehead: emerging sporophyte
• Spore making sporangium on underside of
fronds when reproducing.
Ferns
• Fiddlehead
• Sporangia on
underside of
frond
• Fronds
• Bisexual
gametophyte
Gymnosperms (naked seeds) have no
flowers: gingko, cycad, and conifers
Coniferophyta
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Redwoods, firs, pines, yews, cypresses
Naked seeds: not enclosed in fruits
Wind pollination (NEEDS A LOT)
Seeds, vascular tissue
No flowers
Often needles thick with cuticle and small
in size to limit transpiration.
Seed cones vs. pollen cones
Seed cones
seeds
Pollen cones
Oldest and largest
• Redwoods (400 feet tall)
bristlecone pine (4600 years old)
Anthophyta
• Flowering plants
• Flower will develop into fruit that is used for
seed dispersal via wind, water, or animal.
• Pollination can be by wind, bird, bat, insect.
• Most advanced (recent)
• Gametophyte is reduced and within the
flower.
• Most diverse: grasses to trees
Seed dispersal
Flower structure: reproduction
organ of some plants
Double Fertilization
• Generative nucleus becomes two “sperm” through
mitosis. First sperm fertilizes egg in the ovule and
second sperm fertilizes polar nuclei to become triploid
endosperm. Endosperm will become “food” for seed.
Prefixes for plants
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Mega and Arche are female
Micro and Anther are male
Microgametophyte = pollen (becomes sperm)
Megagametophyte = makes eggs
Atheridium: anthers make male gametes
Archegonium: place where eggs are made
Monoecious (one house) flower
• Name the
parts
• Dioecious:
Two houses/
male and
female
flowers
Parts: functions
• Female (carpel/pistil)
– Stigma is sticky “top” that collects pollen
– Style is connection between stigma and ovary.
– Ovary is where eggs are made in the ovules
• Male (stamen)
– Anther makes the pollen
– Filament holds anther away from female part to allow for
wind/insect to carry pollen away
• Petals (collectively called corona): attracts
pollinators
• Sepals (collectively called calyx); protects the bud
before blooming
Fruit
• The ripened ovary becomes the fruit after
the fertilization of the egg and formation of
the seed.
• Single fruit: one flower with one pistil
• Aggregate fruit: one flower with mutliple
pistils
• Multiple fruit: multiple flowers fuse to
make one fruit
Fruit types
• Simple
aggregate
multiple
Review
• What division of plants has no vascular
tissue?
• What is made by the archegonium?
• What part of the flower “catches the pollen?
• What is one gymnosperm other than
coniferophyta?
• What part of a flower becomes the fruit?
• Where do you find the sporangium on a fern?
More review
• What process makes the gametes in a plant?
• What division of plants includes the tallest
trees?
• What is the purpose of the fruit?
• What is the food of a seed called?
• What group of green algae are the closest
relatives to plants?
• What does the cuticle prevent?
• How many flowers lead to an aggregate fruit?
• What is true of plants that are heterosporous?