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
sporophyt
e
Other Bryophytes
Liverworts
Hornwort
Gametophyte
s
• Antheridium Archegonium
• Male gametophyte
Female
gametophyte
• Makes sperm 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
gametophy
te
Gymnosperms (naked seeds) have
no flowers: gingko, cycad, and
conifers
Coniferophyta
• 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.
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
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
• 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?
