Download Reproduction in Flowering Plants

Reproduction in Flowering
Plants
Objective:
1.
Describe the reproductive organs of the plant
2.
Explain the process of sexual reproduction in angiosperms
3.
Describe the structure and function and structure of seeds
Homework: Learn about and describe different methods of seed dispersal
Review
1. Why are the palisade and the spongy
mesophyll called the ‘working layers’ of the
leaf?
2. What is cambium and what does it do?
3. How does the arrangement of the stomata
leading into the spongy mesophyll (filled
with air spaces) ensure chlorophyll
containing cells have a constant supply of
carbon dioxide for photosynthesis?
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Parts of an angiosperm
Sexual Reproduction in
Angiosperms
• How do plants get to new areas?
– Seeds
• Plants reproduce sexually
• The products of this sexual reproduction are seeds.
• These seeds are contained inside an ovary. Which
develops into a fruit in angiosperms.
• Seeds have two functions
– Protect and nourish the embryo inside
– Carry that embryo to a new location
Reproductive Parts
Male reproductive organs (stamen):
• Anther: produces pollen grains
• Filament: supports anther above
female reproductive organs
Female reproductive organs (carpel):
• Stigma: sticky landing site for
pollen grains
• Style: tube that leads down to
ovary
• Ovary: contains ovules that
develop into seeds
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Reproductive Mechanisms
Pollen (male gamete) from one plant lands
on the stigma of another plant.
This is called pollination.
stigma
pollen
Methods of Pollination
• Natural Reproduction
• Pollination in angiosperms can happen by
wind or animals.
• Animals can transfer pollen (bees) from
one plant to the other.
– They are called pollinators
• Pollen can be blown from one plant to
another.
– Wind dispersal
Pollination
Watch video on reproductive
adaptations.
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Selective breeding in plants
texture
taste
size
Selective breeding and
cross-breeding are
carried out on plants to
produce flowers and
crops with desirable
characteristics…
colour
9A Plant-breeding techniques
Anne the plant breeder chooses two
parent plants with useful characteristics.
One plant will be the female parent.
Anne removes the anthers and covers
the flower with a bag. Why?
female parent
The other plant is the male parent.
Its anthers develop as normal.
Anne collects its pollen and brushes
it onto the female plant.
collected
pollen
anthers removed
She puts the bag over the flower again. Later she collects
the seeds and grows them to produce the new plant.
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From Pollen to Ovary
The pollen grain grows a pollen tube
towards the ovary, which contains the
ovule and egg cell (female gamete).
pollen tube
ovary
containing
ovule
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Fertilization
Fertilisation takes place when the ‘sperm’
nucleus from the pollen grain enters the egg
cell. The resulting zygote eventually turns
into a seed.
pollen tube
with pollen
grain nucleus
ovule
Embryo grows
inside the ovule.
egg cell
Compare
• With your neighbour, discuss how the
reproductive system in plants is similar to
the reproductive system in humans.
Quiz
1. Name three different methods of seed
dispersal.
2. Chose one method and explain how it
effectively disperses seeds away from
plant.
3. What are the male parts of the plant
called?
4. What is it called when pollen from one
plant lands on the stigma of another
plant.
Comparing Plant and Human
Reproductive Systems
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Plant
Male and Female organs
Male Gamete is pollen
Female Gamete is egg
produced in ovule
Pollen nuclei fuses with egg
nuclei (fertiliation)
Diploid zygote
Zygote grows into embryo
Embryo grows inside
protective seed coat
Cotyledons provide
nourishment
•
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•
•
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Human
Male or Female organs
Male Gamete is sperm
Female Gamete is egg
produced in ovary
Sperm nuclei fuses with egg
nuclei (fertilization)
Diploid zygote
Zygote grows into embryo
Embryo grows inside
protective womb
Placenta provides
nourishment
Zygote to Embryo
The zygote will grow
through the process
of mitosis to form an
embryo (The ovule is
now called a seed
and is covered by a
protective seed coat.)
seed
seed coat
food supply
(cotyledon)
embryo
Fruit Formation
• Some plants produce fruit
containing seeds.
• Fruit: Mature ovary
• Tissue surrounding the
embryo develops into
fruit.
• When the fruit is fully
developed it drops off the
plant, or is carried away
by an animal.
• When fruit decomposes it
releases the seed and
germination can occur.
Germination
• A seed requires moisture (water) to germinate.
• The as the embryo grows, the root and shoot
break through the seed coat.
• Nutrients stored in the cotyledon provide
nourishment and support early development
Life cycle of an angiosperm
Asexual Reproduction in Plants…
Watch Video
The stem is the most common organ used in
asexual reproduction.
Results in genetically identical offspring
Requires less energy
Results in less diversity, but diversity may
not be energy efficient or necessary.
Examples…
• Plants such as the
grasses produce
underground stems
called rhizomes.
– Grow through the soil
periodically producing
adventitious roots and
a new above ground
shoot.
• Some plants, like
strawberry plants
grow stems that
produce few, if any,
leaves.
– Stems sprout
adventitious roots
down into the soil,
and new above
ground shoots.
Plantlets…
• Duckweed miniature
plants on the edge of
their leaves. These
drop off and develop
into mature plants.
– Reproduces almost
entirely by this
method.
Plenary..
1. What is the function of the flower?
2. What is a seed?
3. What basic condition is required for a seed
to germinate?
4. Describe two methods of pollination.
H/W Read pages 281-283 in text.
How do gymnosperms reproduce???
How do angiosperms reproduce???
5. Read pp. 307- 309
Complete questions #1-3, 5-7