Reproduction in Flowering Plants:
ASEXUAL: *DNA is identical to the parent (clones)
Plants use this method naturally, they have
developed special structures for asexual “propagation.”
*Bulbs, rhizomes, tubers, corms, runners are all
structures that can form new plants identical to the parent.
SEXUAL: *DNA from male (sperm) and female (egg) is
recombined to produce offspring genetically different
than the parents.
*Flowers developed as the sexual structures
in flowering plants.
*Egg and sperm come together (egg is fertilized)
to produce seeds.
Stigma
Style
Anther
Filament
Ovary
Parts of a flower:
Stamen: Male part
Anther: produces pollen (sperm)
Filament: positions anther
Pistil: Female part
Stigma: traps pollen (sperm)
Style: positions stigma
Ovary: produces egg cells, develops
into fruit
Egg cells: get fertilized by spermdevelops into seeds
Poppy:
Lily: unopened bud
Sexual Reproduction:
Pollination: “Pollen landing on the stigma of a pistil”
The first step in the development of seed.
Reason for Pollination methods:
1. Sperm must travel to the egg (Pistil) of a flower
2. Plants’ movement is limited
3. Must use other methods to move pollen
Methods:
Animal
Wind
Adaptations for Animal Pollination:
1. Size and Colors of petals:
Colors: ie: Red attracts hummingbirds
White flowers that open at night- moths
Patterns that reflect UV light- patterns to
show insects where to land.
Patterns that resemble female insects
2. Fragrance
Sweet: Attracts animals that like sugar (bees)
Rotten: Attracts animals that like rotting meat (flies)
3. Nectar
Reward for pollination- sugar water
Animal
Pollination
http://biology.clc.uc.edu/Courses/bio303/coevolution.htm
How some bees see flowers:
Regular wavelengths
UV patterns
This orchid mimics a female wasp. It also releases
chemicals that resemble the smell of a female wasp.
When male wasps
come to “mate”
with this fake female,
they pollinate the
flowers
Adaptations for Wind Pollination:
1. Lack of petals:
Energy is not spent on producing petals
2. Lack of Fragrance
Energy is not spent on producing these chemicals
3. Lack of Nectar
Energy is not spent on producing sugars
4. Lots of pollen:
Only by chance that pollen lands on the stigma,
produce lots of pollen to increase odds of success
5. Modification of stigma.
Large, Feathery, Sticky- all to increase chance
of catching pollen.
http://biology.clc.uc.edu/Courses/bio303/coevolution.htm
Wind
Pollination
http://www.systbot.unizh.ch/institut/persone
n/person.php?id=23&s=evolutionofwindpoll&l=d
http://images.google.com/imgres?imgurl=http://www.nazflora.org/Asclepias%2520subvert%2520seed%2520dispersal%252025Aug02
.jpg&imgrefurl=http://www.nazflora.org/Asclepias_subverticillata.htm&h=481&w=650&sz=85&hl=en&start=21&tbnid=Iw0eLwJ45l3aBM
:&tbnh=101&tbnw=137&prev=/images%3Fq%3Dseed%2Bdispersal%26start%3D20%26ndsp%3D20%26svnum%3D10%26hl%3Den%26sa%3DN
How would these flowers be pollinated?
http://www.easttennesseewildflowers.com/gallery/view_album.php?set_albumName=Arizona_05
http://www.treemail.nl/kronendak/amazon/assets/photographs%20large/Br
assavola-martiana.jpg
How would these flowers be pollinated?
http://images.google.com/imgres?imgurl=http://www.cas.vanderbilt.edu/bioimages/biohires/a
/hacsa3-fl10386.jpg&imgrefurl=http://www.cas.vanderbilt.edu/bioi
mages/pages/fruit-devel.htm&h=1440&w=960&sz=110&hl=en&start=2&tbnid=bXDGwdl_h3X2uM:&tbnh=150&tbnw=100&
prev=/images%3Fq%3Dwind%2Bpollinated%2Bflowers%26svnum%3D10%26hl%3Den%26sa%3DG
The next steps in SEX and seed production:
1. Development of nuclei in ovule (egg cell)
2. Formation of the pollen tube.
3. Fertilization
Review the female
parts of a flower:
The pistil
Note: the “embryo sac” is
inside the ovule
http://www.jburroughs.org/science/resources/flower/pollination.html
How did the embryo sac get so many nuclei?
2. Egg Cell Preparation for Fertilization
Cell division creates multiple nuclei
in the ovule (egg cell)
http://www.jburroughs.org/science/resources/flower/ovulediagrams.html
Egg cell in ovule
Polar nuclei
in
ovule
Pollination:
Pollen (orange)
lands on the stigma
The “tube nucleus”(green) helps make
enzymes that digest a “tunnel”
through the style (yellow).
The next steps in seed production:
1. Pollen tube development
2. Development of nuclei in ovule(egg cell)
3. Fertilization
2. Pollen tube development:
1. Development of pollen tube down through
the style.
2. Pollen tube is “digested” by enzymes made
by the ‘tube nucleus’ from the pollen grain.
3. Pollen tube forms all the way to the
ovule (egg cell) in the ovary.
4. Sperm nuclei (two of them) follow the tube
nucleus down the pollen tube.
Tunnel (yellow) forms all the way
down to the ovule
Tube nucleus
(green).
Besides the tube nucleus,
the pollen grain also
has TWO sperm nucleiwhich move down the
“tunnel to the ovule
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Angiosperm.html#flower
The next steps in seed production:
3. Fertilization
1. One sperm fertilizes the egg to form the nucleus
2. The second sperm fertilizes two polar nuclei to
form a 3n (triploid) cell.
Removed Ovule
One sperm cell fuses with
the two haploid polar nuclei
to form a triploid (3n) cell. (yellow)
The other sperm
nucleus fuses with
the egg cell (green) in the
ovule to form a
diploid (2n) cell which will
grow into the embryo.
This cell divides many times
to form a tissue called the
“endosperm”. This will be
the food for the embryo.
The ovule will now develop into a mature seed
Parts of the mature seed:
Seed coat
Endosperm and
cotyledon
Parts of the Embryo:
Epicotyl
Radical
Review on line sources:
http://www-plb.ucdavis.edu/labs/rost/Rice/Reproduction/flower/fertiliz.html
http://www.backyardnature.net/frt_mult.htm
From flower to fruit (and seed):
How is the flower below pollinated?
Two flowers fused together
http://www.cas.vanderbilt.edu/bioimages/pages/fruit-devel.htm
Ovaries swell after fertilization
2
1
3
4
MONOCOT seed:
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Angiosperm.html#flower
DICOT seed:
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Angiosperm.html#flower
Seed Dispersal:
Methods to move seeds- why do plants
need to move seeds?
Methods:
1. Wind:
Feathers or wings
2. Water:
Air pockets or floats (bladder)
3. Animals:
Sticky or burrs
Edible fruit
4. Mechanical:
Pod explodes- shooting seeds out
Overview:
Seed Dispersal
Methods:
http://www.nazflora.org/Asclepias%20subvert%20seed%20dispersal%2025Aug02.jpg
Animals:
“Hitchhikers”
http://waynesword.palomar.edu/images/cockle4b.gif
Animals:
Edibles
www.cas.vanderbilt.edu
Animals:
Edibles
http://www.oranim.ac.il/teachers/ido/homepage/Frugivory%
20and%20seed%20dispersal%20papers_files/image006.jpg
Mechanical
http://images.google.com/imgres?imgurl=http://www.cas.vanderbilt.edu/bioimages/i/wimca--fr29363.jpg&imgrefurl=http://www.cas.vanderbilt.edu/bioimages/pages/fruit-seedgVxXmM:&tbnh=84&tbnw=126&prev=/images%3Fq%3DJewel%2Bweed%2Bseed%2Bdispersal%26svnum%3D10%26hl%3Den%26sa%3DG
Water
Germination: Seeds break dormancy
and begin to grow
http://www.botany.hawaii.edu/faculty/webb/BOT410/Angiosperm/Seeds/LegGermSdlingBIODMod.jpg
Factors that affect Germination:
Water: Enough water- too much will block out oxygen
and allow rotting pathogens to attack the seed.
Temperature: Warm temperatures generally speed up
reactions by speeding up molecular motion.
Light: Species specific- some need exposure to light.
some will not germinate while exposed to light.
Scarification: Scaring or cracking the seed coat to
allow water to move into the seed.
Factors that affect Germination:
Stratification: A series of absorbing water followed
by exposure low temperature followed by
warm temperatures.
Fire: Breaks open seed coat allowing water in.