S-20.b How Are Seeds Dispersed?

How Are Seeds Dispersed?

Key Notes :

Seed dispersal is the process by which seeds are spread from the parent plant to new locations where they can germinate and grow.
It helps plants reduce competition for resources like sunlight, water, and nutrients.

Prevents overcrowding around the parent plant.
Increases the chances of species survival by spreading seeds to different environments.
Helps plants colonize new areas, expanding their range.

There are four main methods of seed dispersal:

Wind Dispersal (Anemochory)
- Seeds are carried by wind.
- Examples: Dandelion, Maple, and Cottonwood trees.
- Characteristics: Light, winged, or feathery seeds that can float in the air.
Water Dispersal (Hydrochory)
- Seeds are dispersed by water.
- Examples: Coconuts, Water lilies.
- Characteristics: Seeds can float on water and travel across rivers, lakes, or oceans.
Animal Dispersal (Zoochory)
- Seeds are carried by animals, either by sticking to their fur or being eaten and later excreted.
- Examples: Burdock (seeds stick to fur), berries (eaten by birds or mammals).
- Characteristics: Seeds are often sticky, fleshy, or edible to attract animals. They can be dropped or excreted in a different location.
Explosion Dispersal (Autochory)
- Seeds are scattered when the fruit explodes or opens forcefully.
- Examples: Peas, Violaceae (Violet family), and Witch hazel.
- Characteristics: Seeds are shot away from the plant as the fruit bursts open, often using mechanical force.

Plants have special features that help them disperse their seeds effectively:

Wings or Parachutes: Help seeds float through the air (e.g., maple seeds).
Hooks or Barbs: Allow seeds to attach to animal fur (e.g., burrs).
Fleshy Fruits: Attract animals to eat and later excrete the seeds (e.g., berries, mangoes).
Light and Waterproof Seeds: Help seeds float on water (e.g., coconuts).

Coconut: The large, fibrous fruit floats on water, helping it travel across oceans.
Dandelion: Its light, feathery seeds are blown by the wind, traveling long distances.
Burrs: Seeds with hooks that attach to animals’ fur and are carried to new locations.

Wind: Disperses seeds far and wide without relying on other organisms.
Water: Enables seeds to travel across large bodies of water.
Animals: Provides a way for seeds to travel long distances, sometimes across varied terrain.
Explosion: Effective for plants growing in densely populated areas or where animals cannot easily reach.

Environment: Plants in dry, windy areas may rely more on wind dispersal, while those near water may depend on water dispersal.
Plant Size and Type: Smaller plants may use wind or animals, while larger trees may use explosive or water dispersal.
Animal Behavior: Animals play a significant role in seed dispersal, especially in forest ecosystems.

Dispersal: The movement of seeds from the parent plant.
Germination: The process of a seed growing into a new plant.
Pollination: The transfer of pollen from one flower to another to enable seed formation.

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