Seed Dispersal

Reproduction in plants — getting the flowers pollinated

Plants have adaptations to help them in pollination.

Flowers that are pollinated by animals are usually large and colourful.

They also have nectar and a fragrance so that the animals are attracted to them.

flower pollinated by animals

Reproduction in plants — getting the flowers pollinated

Plants have adaptations to help them in pollination.

Flowers that are pollinated by wind are usually small, plain and without fragrance because they do not need to attract animals.

flower pollinated by wind

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GE2009

From Flower to Fruit

• When all the ovules in a flower have been fertilized, the petals, stamens, stigma and style are no longer needed.

• They will usually wither and fall, leaving an ovary in which the ovules are developing into seeds.

• The fruit protects the seeds. • What is so important about seeds such that

they need protection?

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GE2009

Flower to Fruit

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Pea fruit from flowers

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

The Fruit and the Seeds

• Seeds will grow into new plants and ensure the continual existence of that type of plant.

• However, seeds cannot grow too close to their parent plant. Why?1. OVERCROWDING

- Overcrowding leads to competition for:1. Water2. Space3. Nutrients4. Light

2. Get to grow in new habitats where conditions may be even better.

Before we look at dispersal…

• Take note of the THREE points:

1.Dispersal method of the fruit and the dispersal agent.

2.Characteristics of the fruit that supports dispersal.

3.Dispersal pattern of the fruit.

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

AGENTS OF DISPERSAL

• Seeds and fruits are modified in different ways to be dispersed using one or two of the agents of dispersal.

• Which parts get modified?

An ovule which has been fertilised and become mature. Its wall is the testa.Seed

Fruit A mature ovary which contains fertilised seeds. Its wall is the pericarp

The testa and pericarp are often modified to help in dispersal

Reproduction in plants — getting the seeds dispersed

Flowering plants have different adaptations to enable their seeds to be dispersed as far away as possible.

The different methods of seed dispersal are…

by wind

by animals

by water

by splitting open forcefully

Reproduction in plants — getting the seeds dispersedWhat are the adaptations that help these

fruits/seeds to be dispersed?

angsana

shorea

Dispersal by wind small light dry wing-like

Dispersal by wind small light dry wing-like

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Dispersal by Wind

• Plants which depend on the wind for the dispersal of seeds usually have

light seeds or

wings or

a parachute of fine hairs or

feathery hairs that act like many little parachutes

• to help keep them floating in the air

Dispersal Pattern - Wind

Parent

Wind direction Legend Offspring

Reproduction in plants — getting the seeds dispersed

tomato

Dispersal by animals (eaten) bright colours sweet juicy

Dispersal by animals (eaten) bright colours sweet juicy

What are the adaptations that help thesefruits/seeds to be dispersed?

How about lovegrass? How

does it disperse?

Dispersal by animals (carried)

small hooks stiff hairs

Dispersal by animals (carried)

small hooks stiff hairs

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Dispersal by Animals• Three ways

– First way• The seeds or fruits have hooks or sticky hair that catch

onto the fur of animals or clothing of human beings

– Second way• Fruits get eaten by animals and seeds are thrown onto the

ground as they are too big to be eaten by animals; or• Fruits and seeds get eaten by animals but the seeds are

too hard to be digested by animals and are passed out in the droppings

– Third way• Animals collect the fruits and seeds and take them to their

burrows.

Dispersal Pattern - Animals

Parent

Wind direction Legend Offspring

Reproduction in plants ― getting the seeds dispersed

coconut saga

Dispersal by water

buoyant waterproof air spaces

Dispersal by water

buoyant waterproof air spaces

What are the adaptations that help thesefruits/seeds to be dispersed?

Dispersal by splitting open dry and hard fruit wall

Dispersal by splitting open dry and hard fruit wall

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Dispersal by Water

• Plants which depend on the water for the dispersal of seeds usually have

Some feature that will allow it to float

Some protective covering to protect it during its long water journey.

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Pong Pong

Coconut

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Nipah Fruit

Lotus Fruit Pod

Dispersal Pattern - Water

Parent

Wind directionLegend Offspring

Downstream

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Dispersal by Explosive Mechanism or Splitting of the Fruit

The fruit wall suddenly breaks into several parts and the movement causes the seeds to be shot out. This is caused by the unequal drying up of the fruit wall. The wall may split in one, two or many places along the line/lines of dehiscence (lines of splitting).

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Unripe

Ripe

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Ripe and unripe Kapok fruits

Mrs Theresa Teo GE2003Edited Mr Lin Lixun GEO2009

Dispersal Pattern – Splitting Action or Explosive Mechanism Only

Parent

Wind direction Legend Offspring

Dispersal Pattern – Splitting Action WITH Wind

Parent

Wind direction Legend Offspring

Fruits/seeds • dry and hard fruit wall

Fruits/seeds brightly coloured sweet juicy

by splitting open

Fruits/seeds small light dry wing-like

Fruits/seeds buoyant waterproof air spaces

At a glance…

by wind

seed dispersal

by water

Adaptations for reproduction

plants

Fruits/seeds small hooks stiff hairs

by animals