Plant reproduction

Sexual reproduction

Learning Intentions

I can describe methods of sexual reproduction in plants

I can describe the process of pollination, fertilisation , seed formation and dispersal

Success Criteria

Success Criteria I can state plants use flowers as a method of sexual

reproduction I can put the stages of a plants life cycle in order I can define pollination and fertilisation I can describe how pollination and fertilisation occurs in

plants I can explain how seeds are formed I can describe methods of seed dispersal I can explain the advantages of seed dispersal I am able to label diagrams correctly

Plant Life Cycle

A plants life cycle shows all the stages in a flowers life

From seed to flower And back to seeds

This is plant reproduction

It allows plants to reproduce so new flowers will form again and again

Tomato plant

This flower has been pollinated. Now the fruit, containing seeds, is developing.

Flower

Plant growthFruit and seed development and dispersal

Germination

Tomato plant life cycle

Flower formationPollination and

fertilisation

Parts of a flower Petals – bright to attract

insects Stamen contains the

anther which splits down the middle to release the pollen

Stigma The stigma is the

region to which pollen grains become attached

Nectary – makes sugary nectar which insects eat

Sepals - protects unopened flower

Ovary – female part of the flower that contains the ovules

Arrangement of ovules as seen in cross section of ovary

Pollination

•The pistil is part of the stigma.

•Pollination is the transfer of pollen from the anther to the stigma

Insect pollination

e.g. e.g. Passion Passion flowerflower

Wind Pollination

e.g. Sedgee.g. Sedge

Methods of Pollination

Insect pollination Wind pollination

Have a scent No scent

Sticky, spiky pollen Large amounts of light pollen

Sticky stigma inside flower

Feathery stigmas hang outside the flower

Stamens surrounded by petals

Large stamens hang outside flower

Produce nectar Don’t produce nectar

Petals large & bright Petals small & dull

Fertilisation Once the pollen grain lands on the stigma, it

grows a pollen tube down to the ovule.

Fertilisation is when the nucleus of the pollen grain fuses with the nucleus of the ovule

The fertilised ovule develops into a seed

The ovary wall develops into the fruit.

Seed dispersal Following pollination and

fertilisation seed formation and dispersal takes place

Seed Dispersal – this is where seeds are scattered away from the parent

Seeds are scattered to avoid competition for water, light and nutrients

Animal (external)

Seeds can be dispersed by animals.

The seed has hooks which catch onto animals’ fur and are transported by the animal until they fall off and hopefully germinate elsewhere.

E.g. Burdock

Animal (internal)

Seeds can also be eaten by animals along with the fruit.

The seeds pass through the animal and are deposited in the droppings elsewhere

E.g. bramble

Wind Dispersal

Plants can also use the wind to scatter their seeds and they use different mechanisms to achieve this.

E.g. the poppy uses the “pepper pot” method

Wind Dispersal

Ragwort, dandelions, cotton, etc. use the “parachute” method.

Each seed has a number of small feather-like structures to help it float in the wind.

Wind Dispersal

Some seeds have wings to help them fly in the wind.

E.g. sycamore, ash, etc..

Explosive

Some plants such as peas and gorse use pods which “explode” to fire the seeds away from the parent.

As a pod dries, tensions are set up in the wall of the pod eventually causing it to split along two lines of weakness.

Advantages of seed dispersal

It reduces competition for resources eg. light, water and mineral nutrients

It reduces the spread of disease

It allow plants to grow in a wider area so more likely to survive in event of a flood or fire.

Seed germination With water, oxygen and the right

temperature the seed swells and begins to make a new plant

Germination occurs Stems grow up towards the light, leaves

unfold to take more sunlight and roots anchor the plant

Growth