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“Yesterday is history. Tomorrow is a mystery. Today is a gift. That’s why we call it ‘The Present’.” – Eleanor Roosevelt

Seed Dispersal


 

If all seeds of a plant fall under the parent plant they will grow crowded together and many will die because of lack of space or air, water, sunlight and minerals. Therefore, it is better seeds getting scattered far and wide and have a better chance of growing in a suitable place without over crowding. So, this is what we understand as seed dispersal. Let’s talk about seed dispersal through this lesson. Go to ‘Seed Dispersal Quiz 1’ and ‘Seed Dispersal Quiz 2’, at the end of the lesson and check your knowledge in seed dispersal.

 

What are the main factors (conditions) that plants need to grow?

 

  • Sunlight
  • Water
  • Space or air
  • Warmth
  • Minerals

 

What is seed dispersal?

The scattering or spreading of seeds to different places is called seed dispersal.
Examples of seed dispersal by wind;

 

seed dispersal dandelion

 

seed dispersal thistle

 

seed dispersal oleander

 

What are the special features in seeds to disperse seeds?

 

1) Some seeds are sticky and have hooks.

2) Some seeds have wings.

3) Some seeds have hairy parachutes.

4) Some seeds are in pods.

5) Some seeds have small holes in them.

6) Some seeds have spongy layers of fibres around them.

7) Some seeds have smaller spongy coverings.

 

Examples of the special features in seeds for seed dispersal

Sticky and have hooks Wings Hairy parachutes Pods Holes Spongy layers of fibres Spongy coverings
Goosegrass sycamore Dandelion peas Poppy Coconut Water lilies
Burdock ash thistle lupins orchid   Alder tree
Woodavens maple   laburnum      
  lime   gorse      

 

seed dispersal dandelion

Example of seed dispersal by wind
A dandelion seed dispersed by the wind

seed dispersal thistle

 

seed dispersal thistle seeds

Examples of seed dispersal by wind
A dried thistle has many seeds with hairy parachutes which can be dispersed by wind

 

 

seed dispersal sycamore

 

seed dispersal sycamore seeds parts

Examples of seed dispersal by wind
This is a dried sycamore fruit which bears many seeds with wings which can be dispersed by wind

 

Who are the agents of seed dispersal?

 

  • Wind
  • Water
  • Animals

 

seed-dispersal-water

 

 

seed dispersal seed dispersal by wind

 

 

Examples of seed dispersal

 

By wind

 

Examples of seed dispersal by wind;

 

Seeds which have wings and hairy parachutes on them are carried by the wind.

E.g. – sycamore, ash, maple, lime, dandelion and thistle

 seed-dispersal-lime-tree

 

When pods dry, they split open suddenly and shooting the seeds away from the parent plant and this is easy when the wind is there.

E.g. – peas, lupins, laburnum and gorse

 

Some seeds have small holes in them, so they are very light in weight. When the wind rocks the plant, the seeds are scattered as if from a pepper pot.

E.g. – poppy and orchid fruits

 

By water

 

Examples of seed dispersal by water;

 

Some seeds have spongy layers of fibres around them. These can trap air so the seeds can float.

 

These seeds can travel, sometimes for hundreds of kilometers, from one island to another.

E.g. – Coconut

 

seed dispersal coconut tree

 

Some seeds have smaller spongy coverings which lets them float in lakes and rivers.

E.g. – water lilies, alder trees

 

By animals

 

Examples of seed dispersal by animals;

 

Brightly coloured and juicy fruits are often eaten by animals like birds. The hard seeds inside these fruits pass out of the animal’s body in its droppings.

E.g. – blackberries, strawberries, raspberries and gooseberries

 

The seeds may finish up a long way from where they were first eaten.

Animals like squirrels and jays bury some nuts, ready to eat later. These animals often forget where they have hidden their food, and some of these seeds can grow.

 seed dispersal squirrels birds

 

Some seeds and fruits have hooks that catch on the fur or feathers of animals or on people’s clothes. If the seeds eventually drop off on the soil, they may grow.

E.g. – goosegrass, burdock, wood avens

 

Examples of seed dispersal by humans;

 

seed dispersal by people

Examples of seeds with hooks that catch on people’s clothes and shoes

 

Try Seed Dispersal Quiz 1 and Seed Dispersal Quiz 2