FLOWERS AS REPRODUCTIVE STRUCTURES

ABBOTTS

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FLOWER STRUCTURE PAGE 53

Parts of a Flower

Stigma

Style

Ovary

Carpel/Pistil

(female) Anther

Filament

Stamen (male)

petals

ovule

sepal

DIAGRAM PAGE 53

Parts of the Flower

Peduncle: flower stalk Receptacle: part of stalk bearing the floral organs, at base

of flower Sepal: leaflike structures at flower base, protects young

flower bud Calyx: all the sepals together form the calyx Petal: located inside and above the sepals, often large and

colourful, sometimes scented, sometimes producing nectar Stamen: male part of the flower, consist of the anther and

filament, makes pollen grains Pollen: grains containing the male gametes Pistil/Carpel: female part of the flower, consist of the

stigma, style and ovary Ovule: located in the ovaries, carry female gametes

FLOWER ANATOMY

Anther

Sepal

Filament

Petal

Stigma

Pollen Tube

Ovary

Style

Ovule

Stamen

Carpel

PURPOSE OF EACH FLOWER PART

A. Carpel:

1. Stigma- Covered in a sticky substance that pollen grains can stick to

2. Style- Raises the stigma away from the ovary to decrease pollen contamination

3. Ovary- Protects the ovule after fertilization; becomes the fruit

4. Pollen Tube- What the pollen travels through to reach the eggs in the ovule

5. Ovule- Like the egg in animals; once fertilization takes place it will become the seed.

PURPOSE OF EACH FLOWER PART

B. Stamen:

Anther- Contain pollen sacs. The sacs release pollen on to the outside of the anthers where wind or other organisms can transfer the pollen to the carpel for fertilization.

Filament- Stalk of the anther

C. Petal: Petals are used to attract insects into the flower, they may have guidelines on them and be scented.

D. Sepal: Sepals protect the flower whilst the flower is developing from a bud.

FLOWER FUNCTIONS

Flowers contain the reproductive organs Stamens – male parts Carpel – female part

Flowers attract pollinators who transport pollen from the anther to the stigma

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TO DO

DRAW FLOWER IN YOUR

WORKBOOKPAGE 53

DRAWING11

Use a sharp HB pencil Drawing must be big enough e.g. Half a page Leave enough space around the drawing for labels Labels must be written in ink and not cover the diagram

itself Label lines must be in ink, drawn with a ruler and must

not cross each other The line must not end with an arrow and it must indicate

the exact part that is being labelled The drawing should have a heading stating what the

diagram shows

POLLINATION BY POLLINATORS

Pollinators are organisms that aid in the transfer of pollen from anther to stigma, to allow for fertilization

Flowers get pollinated and pollinators get food

ADD TO WORKBOOK

Pollination takes place through:

insectswindbirdswater

POLLINATION

13

Is the transfer of ripe pollen containing the male gametes from the anthers to the stigma to allow for fertilization

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14

Self Pollination = when the pollen from one flower is used to fertilize the eggs produced by that same flower; true-bred flowers

15

Cross Pollination = when the pollen from one flower is used to fertilize a different flower of the same type

POLLINATION BY POLLINATORS

Pollinators are animals that move pollen from anther to stigma, to allow for fertilisation

Pollinators visit flowers to get food (pollen and nectar)

Flowers get pollinated and pollinators get food Pollinators are mostly insects (some are

vertebrates)

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ADAPTATIONS OF INSECT-POLLINATED FLOWERS

The flowers have large conspicuous petals in bright colours

Sweet scent to attract moths and butterflies Offer a reward of nectar and/pollen Anthers and stigma are often inside the flower Pollen grains are often sticky or spiky (stick to the

insects Large quantities of pollen are produced Flowers have nectar guides to help the insect find

the centre of the flower

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SOUTH AFRICAN INSECT-POLLINATED FLOWER

Bluish in colour – bees pollinate blue and yellow flowers

Delicate sweet scent Sturdy with a landing platform

on which the bee lands Have nectaries which secrete

nectar (sweet liquid) to attract and feed pollinators

Flowers are open in the daytime

Pollen grains stick to the bodies of bees

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Salvia africana-caerulea

ADAPTATIONS OF BIRD POLLINATED FLOWERS

Flowers produce a large quantity of dilute nectar Flowers are bigger than insect pollinated flowers Flowers are red and open in the daytime Flowers are sturdy – birds are rough Flowers have little or no scent – birds have a poor

sense of smell Ovules are protected from the probing beaks Pollen grains stick together in clumps – bird picks up

a lot of pollen in one visit Flowers are erect with a landing platform

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SOUTH AFRICAN BIRD-POLLINATED FLOWER 

Flowers stand at the tips of long stalks

Flowers have a sturdy landing place for sunbirds

Flowers have three orange sepals and three blue petals

Two of the petals join together to form a dart to hold the stamens, style and nectary

Dart provides a perch for the sunbird

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strelitzia reginae

The structure and pollination of the flowers is fascinating. The hard, beak-like sheath from which the flower emerges, is called the spathe. This is held at right angles to the stem, and has the appearance of a bird's head. Each spathe contains 4 to 6 flowers, and these emerge one at a time from the spathe. Each flower consists of 3 clear yellow sepals and 3 deep purple petals. The yellow sepals give the appearance of a crest on the 'bird's' head. Two of the purple petals are joined together around the stamens and the style to form an arrow-like structure. The third purple petal is visible as a small scale.

EXTRA STUFF

DART FORMED BYBLUE PETALS

SEPALS

SPATHE

ADAPATATIONS OF A WIND-POLLINATED FLOWER

Small, inconspicuous flowers without any bright petals

Petals are often absent for better exposure to wind

No nectar or produced No scent Male flowers are often arranged in

catkins (clusters) that move freely in the wind

Long thin filaments hang outside the flower, easily shaken by the wind

Anthers are large and well exposed to catch the wind

Pollen grains are small (non sticky) and light and easily carried by the wind

Stigmas are long and feather- like with a large surface area and outside the flower to trap pollen

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Examples of inflorescence types.

An inflorescence is a group or cluster of flowers arranged on a stem

WORKBOOK

SOUTH AFRICAN WIND POLLINATED FLOWER

Simple flowers with all the features of wind pollinated flowers except the anthers are not visible

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Thamnochortus pellucidus in flower

Female inflorescence Male inflorescence

The male infloresence hangs down on a flexible stalk to shake the pollen free

Wind distributes the pollen to the female infloresence – caught by bracts and directed to hidden female flowers

Insect Bird

Shape of flower Corolla tube wide and often horizontal – suits approach flight of insectsLanding platform present

Corolla tube often long and narrow to suit shape of birds beakNo landing platform

Colour Not red- bee deterrent Often red – bird attraction colour

Corolla Not large or strong Larger and stronger

Nectar Less nectar- stronger concentration

Much dilute nectar

Nectar guides Present – insect vision not good

Absent – bird has excellent vision

Scent yes Never

Night blooming Sometimes – moths pollinate at night

never

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DIFFERENCES BETWEEN BIRD AND INSECT POLLINATED FLOWERS

SIMILARITIES BETWEEN BIRD AND INSECT POLLINATED FLOWERS

Produce less pollen than wind pollinated flowers; there is no wastage as the pollen is taken directly between plants

Both produce nectar Have pollen grains with spikes etc so that they stick

together and can attach easily to the pollinator Have stigmas and anthers either just outside or inside

the flower Might be affected by disease organisms that are

carried to the flower along with pollen Have obvious petals

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Feature Pollinator eg bird/insect

Wind

Shape of flower Conspicuous inconspicuous

Flower ObviousUsually quite large, coloured scented petals

inconspicuous

Stigma Often inside the flower Large feathery stigmas, outside

Stamens Often inside the flower Large stamens, always hang outside

Pollen Fewer pollen grains, which have spikes to stick together in clumps

A lot of small,dry light pollen grains

Pollination process Not wasteful Random and wasteful

Disease transfer Disease organisms can be transferred with the pollen

No disease transfer

Energy expenditure Great – used for pollination, formation of nectar, etc

Less, only used to produce pollen

Scent and nectar Can be present No scent or nectar

PAGE 59DIFFERENCES BETWEEN POLLINATOR AND WIND POLLINATION

TO DO

TEXTBOOK PAGE 61

LEARNING ACTIVITY 18

ADAPTATIONS OF FLOWERS FOR POLLINATION

FERTILISATIONDIAGRAM PAGE 62

Fertilisation is the combining of nuclei of a male and female gamete to form a zygote

POLLINATION

33

Is the transfer of ripe pollen containing the male gametes from the anthers to the stigma to allow for fertilization

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WHAT HAPPENS AFTER FERTILISATION?

The zygote forms an embryo inside the ovule

The rest of the ovule forms endosperm (food for the germinating seed)

The outer layer of the ovule forms the testa (hard, dry, protective layer)

The mature ovule = seed

WHAT HAPPENS AFTER FERTILISATION?

The ovary grows and encloses and protects the seeds =fruit

TO DO

TEXTBOOK PAGE 62

LEARNING ACTIVITY 19

POLLINATION AND FERTILISATION

THE END