Seed Dispersal / Fruit Dispersal

Plants disperse their seeds away from them so as to increase their chance of survival.

When seeds are dispersed near the parent plants, they will most probably germinate into young seedlings.

However, these young seedlings would then have to compete for four factors, namely :

1. water

2. nutrients

3. light and

4. space

This is so because, at the first stage of germination, when it is just a seed, it only requires Water,

Oxygen and

Warmth (or right temperature).

The seed at this stage obtains its food from the seed leaves.

At the second stage, when the first root appears, it requires

Water,

Oxygen,

Warmth (or right temperature) and

Edaphic (soil conditions which include porous soil and presence of humus).

At the final stage of germination, before it becomes an adult plant, it requires

Water,

Oxygen,

Warmth (or right temperature),

Light and

Edaphic (soil conditions which includes porous soil and presence of humus).

It is quite easy to notice certain features found in the seeds/fruits of a plant which help them to be dispersed.

(A) Seeds that are dispersed by wind have the following characteristics :

1. light

This allows the seeds to be carried in the air for a longer time before they

land on the ground. Seeds that are light are usually dispersed far away

from their parent plants and thus this increases their chance of survival.

Eg : Vernonia

→

Flowers Seeds are light and can be

blown away by wind

2. have wing-like structures

These wing-like structures or ‘wings’ enable the seeds to be carried further

away from their parent plants.

Eg. Angsana

(B) Seeds dispersed by water have certain characteristics.

1. They usually have fibrous husks. These fibrous husks have air

spaces in them that help them stay buoyant (able to float).

2. They must also be waterproof to stay buoyant.

Eg : Coconut

Fibrous husk

Eg ; Nipah

(C) Seeds that are dispersed by animals have the following

characteristics :

1. They are usually fleshy, sweet and colourful. These features help

them to attract animals to feed on them. The seeds are usually very

hardly and will not be harmed by the digestive juices of the

animals’ stomach. These seeds will then be passed out together

with their droppings.

2. Some fruits and seeds are not brightly coloured, sweet and fleshy. They

have some structures to help them :

- hook-like structures to attach to the clothes of humans or fur of animals

When noticed, these seeds will be pulled out from the clothes or fur and disposed off further away from their plant plants. When they fall on good soil and when the conditions are right, they will germinate into seedlings.

Eg. mimosa fruits

Fruit of mimosa with stiff hair

(D) Some fruits and seeds are dispersed by explosive action

(or splitting)

These fruits are usually in the form of a pod.

A pod-like fruit has certain lines on them.

These are the places where the fruit split open.

Eg. Rubber fruits and lady’s finger

Notice the lines.

This pod-like fruit

splits open when

dry.

Rubber fruit and seeds

Notice

the lines

Lady’s finger

(E) Some fruits and seeds are dispersed using more than one method.

Eg. African Tulip

A bird feeding on the nectar of the

flower and at the same time helping

to pollinate the pollen grains.

The fruit pod of the African Tulip

The fruit splits open and creates a force to

throw out the seeds.

The wing-like structure

enables the seed to be

carried away by wind.

Hence, the African Tulip fruit splits open and throws out the seeds at first.

The wing-like structure enables the seeds to be carried away by wind.

Always remember that an organism reproduces to ensure the continuity of its own kind.