Sexual Reproduction in Flowering Plants

Asexual reproduction (definition)

Does not involve the fusion of gametes

Sexual reproduction (Definition)

Involves the fusion of male and female gametes

Flowers (Definition)

Reproductive organ of a flowering plant

Where does the flower sit?

Receptacle

What is the receptacle?

Swollen stem tip

Draw a diagram of the structure of a flower

What does the ovule contain?

Female eggs

What does the nectary contain?

Sugary fluids to reward pollinators for dropping pollen in stigma

Function of sepals

Protect flower before it blooms

Function of petals

Attract animal pollinators

Stamen function

Male part of the flower

Function of anther

Produces pollen grains that produce male gametes

Filament function

Provides nutrients to anther

Carpel function

Female part of flower

Stigma function

Traps pollen

Where are female gametes produced?

Embryo sac in the ovule

Draw a diagram of an ovule in a carpel

Draw a diagram of pollen grains in an anther

What does each anther contain?

Four pollen sacs

What does each pollen sac contain?

Diploid microspore mother cell (Pollen mother cell)

Function of the tapetum

Nourishes pollen cells

What happens to each microspore mother cell?

Divides by meiosis to produce four haploid cells which are the pollen grain

What happens to each pollen grain?

Divides by mitosis to produce 2 nuclei. One is the tube nucleus and the other is the generative nucleus

Function of tube nucleus

Forms pollen tube

Function of generative nucleus

Fuses with egg

After pollination what happens to the generative nucleus

Divides to produce two male gametes

What does each ovule contain?

Nucellus

What is inside the nucellus?

Embryo sac mother cell

What happens to the embryo sac mother cell

Divides by meiosis to produce 4 haploid cells. Three of the cells disintegrate

What is the remaining cell from the divided embryo sac mother cell called?

Embryo sac/ megaspore

What happens to the embryo sac?

Divides thrice to form 8 haploid nuclei

Functions of the nuclei produced by the megaspore?

One is the egg cell. Two polar nuclei. Others are useless

What will the wall of the ovule turn into?

Seed coat/ Testa

Cross-pollination (Definition)

Transfer of pollen from an anther of one flower to a stigma of a flower of a different plant of the same species

Benefit of cross-pollination

More variety than self-pollination

Benefit of more variety in plants

Better chance of survival and are more resistant to disease

Name 2 agents of pollination

Animals. Wind

How do animal-pollinated flowers attract animals (4)

Brightly coloured petals. Scent. Nectar (energy rich food). Pollen (protein rich food)

Features of wind pollinated flowers (4)

Stigmas feathery to trap large amounts of pollen. Do not have bright colours. Produce large amounts of pollen. Pollen is light to make it easier to carry

Draw a diagram of a wind-pollinated flower

Between where does the pollen tube connect

Style to micropyle

What is the pollen tube attracted to?

Chemicals secreted by ovary and ovule

Draw a diagram of the events leading up to fertilisation

What happens to the two male gametes once they enter the ovule?

One fuses with egg cell to produce zygote. Other fuses with two polar nuclei to produce triploid endosperm nucleus

What does the zygote develop into?

Embryo plant

What does the endosperm develop into?

Food supply for developing embryo

What does the embryo plant consist of?

Plumule. Radicle. Cotyledon

What is the plumule?

Embryo shoot

What is the radicle?

Embryo root

What is the cotelydon?

Food supply for embryo

What does the seed release?

Auxins to cause fruit to form

What type of seeds are monocots classed as?

Endospermic seeds

Why are monocots endospermic?

Store food in endosperm

What type of seeds are dicots classed as?

Non-endospermic seeds

Why are dicots non-endospermic?

Dicots use up their endosperm before the seed is mature

Draw a non-endospermic seed

Draw an endospermic seed

Functions of fruit (2)

Protect seed. Allow for seed dispersal

Benefits of seed dispersal (2)

Prevent competition. Allow plant species to colonise new areas

Four methods of seed dispersal

Wind. Water. Animals. Self-dispersal

Feature of seed/fruit to aid in dispersal (Wind)

Light and may be winged

Feature of seed/fruit to aid in dispersal (Water)

Air spaces/light to increase buoyancy

Feature of seed/fruit to aid in dispersal (Animals)

Sticky/tasty to stick to animal or get egested

Feature of seed/fruit to aid in dispersal (Self)

Pod to release seeds

Example of wind dispersed seed

Sycamore

Example of water dispersed seed

Water lillies

Example of animal dispersed seed

Raspberries

Example of self dispersed seed

Peas

Dormancy (Definition)

Period when a seed does not germinate despite favourable conditions being present

What are seeds that keep their ability to germinate called?

Viable

Advantages of dormancy (3)

Protection from adverse conditions. Allows for immature embryo of seeds to ripen. Allows more time for seeds to be dispersed

Advantages of dormancy for agriculture and horticulture (2)

Allows grower to provide optimal conditions. Allows grower to decide when to sow seeds

Germination (definition)

The regrowth of the embryo plant following a period of dormancy

Requirements for germination (3)

Water. Oxygen. Suitable temperature

Why does a suitable temperature need to be present for germination?

Affects enzymes which are dependent by temperature

What are the two main events that occur during germination?

Digestion of food stores. Respiration and cell division

Where do cotelydons remain during germination?

Below the soil

How does the plumule emerge during germination?

Hooked

Why does the plumule emerge hooked during germination?

Protection from adverse conditions. Allows for immature embryo of seeds to ripen. Allows more time for seeds to be dispersed

Explain Epigeal germination

Cotelydons more above soil and discards pericarp. Plumule emerges between cotelydons to form first two leaves