Transcript FLOWERS AS REPRODUCTIVE STRUCTURES

Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
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The stamens are the
male organs and
produce pollen that
contain the male
gametes
The pistil with the
stigma, style and
ovary is the female
organ of the plant.
The ovulums are
found in the ovule.
Lorraine Kuun, July 2011
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Stamens consist of an
anther with a filament.
The anther produces
pollen in the pollen
sac.
The pollen grains
contain the male
gametes.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
1. Self pollination
2. Geitonogamy
3.Cross-pollination
Lorraine Kuun, July 2011
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Most pollinators are
insects e.g. Bees,
moths, butterflies,
beetles.
Some vertebrates
also pollinate
flowers e.g. Bats,
mice, birds (mainly).
Many flowers are
pollinated by wind.
Lorraine Kuun, July 2011
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Bright colours (bees cannot see red), white for
night pollinators e.g. moths
Often sweet scent (attracts moths and
butterflies)
Reward of nectar and pollen
Contrasting markings on petals to locate
centre of flower (usually not visible to human
eye – ultraviolet)
Pollen cling to hair on insect bodies
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Stamens form “lever”
Pistil overhanging
landing platform
Tubular shape,
contains nectar
Nectar guides
Landing platform
Bees attracted to blue and yellow flowers
Lorraine Kuun, July 2011
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High yield of dilute nectar
Bigger than most insect-pollinated flowers
Open in daytime, often red
Sturdy against rough feeding of birds
Little or no scent – birds have poor sense of
smell
Protect ovary against beaks by being inferior
or by partition
Pollen sticks together in clumps
Often erect or with landing platform for birds
that do not hover
Lorraine Kuun, July 2011
Stigma close to pollen
Stamens fused in
tube to fit beak
Bright colours
Nectaries
Sturdy landing platform
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
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Flowers do not have scent, nectar or brightly
coloured petals – no need to attract
pollinators.
Flowers high on plant to be exposed to wind.
Flowers usually small and reduced, lacking
calyx or corolla (sepals and petals).
Anthers large and well-exposed.
Masses of light, non-sticky pollen produced.
Stigmas long and feathery with large area for
trapping pollen.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
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Meiosis occurs in the
pollen grain.
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The male gametes
are haploid.
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When the ripe pollen
grain lands on a
receptive stigma, it
will germinate.
The pollen grain
germinates and form
a pollen tube.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
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The ovary contains
the ovule(s) with
female gametes (n).
The pollen tube
grows down the
style, through the
micropyle and into
the embryo sac.
Double fertilisation
occurs.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
The ovary develops into the fruit, the
ovule into the seed.
 The
fruit
develops from
the following
layers:
• Fruit wall from
ovary wall.
• Seed from ovule.
Lorraine Kuun, July 2011
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A seed
consists of a
1. Seed coat –
outer layer of
ovule (pericarp).
2. Embryo – from
fertilisized egg
cell (zygote
undergoes
mitosis).
Lorraine Kuun, July 2011
Endosperm
– result of
double
fertilization.
Endosperm
is food for
embryo –
also why we
eat seeds
for food.
Lorraine Kuun, July 2011
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The cotyledons
contain food for
the embryo in
some seeds.
In beans the
cotyledons are
responsible for
photosynthesis
after germination
before first leaves
are formed.
Lorraine Kuun, July 2011
MONOCOTYLEDON
Lorraine Kuun, July 2011
DICOTYLEDON
Lorraine Kuun, July 2011
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Resistant to unfavourable conditions as they
have seed coat.
Can be dispersed effectively (see later).
Can remain viable in dormant state for long
periods.
Seeds have stored food reserve in endosperm
or cotyledons; includes starch, oils and or
protein.
Important to man as they are cheap form of
plant propagation, way to store plants and
are a store of food.
Lorraine Kuun, July 2011
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Dormancy is a state of rest. Embryo inactive,
seed will not germinate.
Some plants have obligatory period of
dormancy – seed will not germinate even if
conditions are favourable.
Dormancy prevents seeds from hatching in
wrong season when seedlings would be
exposed to unfavourable conditions. Allows
seeds to survive unfavourable conditions.
Allows for seed dispersal agents to act.
Lorraine Kuun, July 2011
Wind – seeds are light with plumes or
wings.
 Animals – hooks and thorns – cling to
wool, stick in paws.
 Animals – edible fruit – seeds egested
in different position.
 Water – seeds contain oil or air
bubbles – float away.
 Self-dispersed – fruit dry, dehiscent.
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Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
COCO DE MER drifts
along ocean currents
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
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Most important plant source of food for
humans.
Practical form of food – easy to transport and
store for long periods of time.
Grains – wheat, maize (mealies), sorghum,
rice, oats; mainly starch
Pulses (legumes) – beans, peas, soy beans,
peanuts, lentils, plant proteins
Nuts – oily seeds in hard shells e.g. walnuts,
cashews, pecans etc.
Lorraine Kuun, July 2011
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Many plant species under threat.
Seed bank stores seeds of wild plants and crops.
UK – conserves seeds of about 10% of wild plant
species at Kew – Millennium Seed Bank Project.
Swedish International Seed Vault – reinforced
concrete tunnel – 4,5 million seed samples – will
remain viable for 1000’s of years.
MSBP working with SA National Biodiversity
Institute – contributing 2500 indigenous species
– endangered, endemic, over-exploited
Lorraine Kuun, July 2011
Offer protection against loss of species in
wild due to:
1. Habitat loss – agriculture, development of
cities, building of dams, large-scale
ecological disasters etc.
2. Climate change
3. Over-exploitation of certain species
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Lorraine Kuun, July 2011
Can be used to
1. re-establish damaged, lost
habitats and ecosystems
2. re-introduce extinct, endangered
or threatened species
3. provide research material
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011