Transcript Plant Reproduction and Development

Angiosperm Reproduction and
Biotechnology
Dillin Snape
Overview
• Sexual VS asexual
reproduction.
• Growth of a seed and fruit
• Since agriculture started,
breeders have genetically
manipulated traits of
some wild crops by
artificial selection.
• Now the speed and
extent of plant
modification have
increased in recent
decades with Genetic
Engineering.
Flower Structure
•
Four modified leaves called floral
organs:
– Sepals
• Enclose and protect the floral
bud before it opens.
– Stamens
• Reproductive organ.
• Stalk and anther.
– Carpel
• May have one or more
carpels.
• Ovary at the base
– One or more ovules
inside.
• Long slender neck called the
style.
– At the top there is a
sticky structure called
stigma.
» Landing platform
for pollen.
Pollination Enables Gametes to
Come Together Within a Flower
• Angiosperm sporophytes have
a flower, a reproductive
structure.
• Pollination brings a male
gametophyte to the stigma of a
flower.
• Germination brings a sperm
from the gametophyte to a
female gametophyte.
– Located in the ovule,
embedded in the ovary of
the flower.
• Fertilization happens within
each ovule.
Gametophyte Development and
Pollination
•
•
•
•
•
Male gametophytes form in the
pollen sac.
Female gametophytes forms in
each ovule.
Pollination is transferring pollen
from an anther to a stigma.
A pollen grain makes it way down
to the ovary.
– Discharges sperm to a embryo
sac.
– An embryo develops.
• The ovule develops into a
seed.
– The ovary develops into a fruit
which contains one or more
seeds..
When the conditions are ready
they develop into seedlings.
Preventing Self-Fertilization
• Sexual reproduction has
many advantages.
– Genetic Diversity.
– Better chance of some
offspring surviving a
challenge.
• Self-Incompatibility
– A plant rejects it’s own
pollen by not growing the
pollen tube.
– Gametophytic selfincompatibility.
– Sporophytic selfincompatibility.
After Fertilization
•
•
•
•
Double Fertilization
– One sperm makes a zygote.
– The other sperm make a triploid
nucleus called an endosperm.
• Food storing tissue of the
seed.
Ovules turn into seeds.
Ovaries turn into fruit.
– Protect seeds.
– Aids in dispersal.
Types of fruit
– Simple – From a single carpel or
fused carpel's.
– Aggregate – A single flower with
more than one separate carpel
forming fruits.
• All clustered together.
– Multiple- A group of flowers
clustered together. When the
ovary’s grows they all fuse
together to form one fruit.
Seed germination
•
•
Dormancy
– As it matures it enters a phase of
low metabolic rate.
– Waiting for the right condition to
germinate
The right conditions
– Many species differ, some
example:
• A lot of rain (Desert)
• Forest fire (Competing plants
are gone)
• The right season (Ensuring
a long growth season)
• Light (Lettuce)
• Weakened by chemicals
(Animals digestive tract)
– Some seeds can remain dormant
for days to decades, some even
longer.
Seed to Seedling
•
•
•
Begin by a process called Imbibition
– Uptake of water from the low water
potential of the dry seed.
The first organ to emerge form the seed is
the radicle
– Embryonic root.
Then there are two ways for the shoot tip to
break through the soil surface.
– First Way
• A hook shape forms from the
hypocotyl.
• Growth pushes the hook above
the surface.
• Light stimulates it to straighten.
• Leaves emerge and start making
food from photosynthesis
– Second Way
• The coleoptile, pushes upwards
through the soil and into the air.
• The shoot tip grows through the
tubular coleoptile. Breaking
though the tip.
Asexual Reproduction
• Exact clone of the parent
• Advantages
– If it is in a stable environment
then all of it’s offspring will be
suited for that environment.
– Offspring aren’t as frail.
• Usually mature vegetative
fragment from the parent
plants.
• Disadvantages
– An unstable enviroment
• New pathogens
• Varied offspring means some
can survive.
– If a catastrophic event
happened like a new disease,
then all of them would die.
Mechanisms
•
•
•
•
Plants are able to renew or
sustain growth indefinitely.
Parenchyma cells can divide and
differentiate into more specialized
types of cells.
– A stem can get cut off and it
will grow roots and become a
whole plant.
Fragmentation
– Separation of a parent plants
into parts the develop whole
new plants.
Apomixis
– Producing seeds without
pollination.
– No joining of sperm and egg.
• A diploid cell in the ovule
gives rise to an embryo.
Vegetative Propagation and
Agriculture
•
•
•
•
Propagation is a form of asexual reproduction which
plants grow new roots.
Cutting
– Cutting of parts of a plant that will grow
adventitious roots and form a whole new
plant.
– A callus forms first and then the roots grow
from that.
• If a node is included in the fragment
then the callus stage is skipped.
Grafting
– A twig or bud from one plant can be grafted
onto a plant of a closely related species.
• Combines the best qualities of each
– The plant that provides the root system is the
Stock.
– The grafted part of the other plant is called the
Scion.
Test Tube Cloning
– Able to grow whole plants by culturing smalls
pieces of tissue or even single parenchyma
cells.
– Callus's form and hormones are used to shoot
out roots.
– Then transferred to soil.
– Can make transgenic plants by inserting
foreign genes.
Plant Biotechnology Transforming
Agriculture
• Two meanings:
– Innovations in the use of plants, or the
substances made by plants, to make products
for humans.
– Genetically modifying plants in agriculture and
industry
Artificial Selection