Seed Dispersal: Methods, Benefits & Examples

Seed Dispersal: Methods, Benefits & Examples
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  • 0:04 What is Seed Dispersal?
  • 0:49 Types of Seed Dispersal
  • 1:02 Gravity and Force
  • 2:19 Wind and Water
  • 4:04 Animals and Humans
  • 5:16 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb
Seeds are the offspring of plants. But unlike animals, plants need to spread their seeds away from the parent to propagate their species. In this lesson, we'll be learning the five main strategies plants use to do this.

What Is Seed Dispersal?

Most of us know that humans and animals reproduce sexually. However, did you know that plants reproduce sexually, too? In the spring, the yellow pollen that coats your car is actually plant sperm. So if you have spring allergies, you're actually allergic to plant sperm! That pollen travels to other flowers and fertilizes the ovary. The ovary develops into seeds. Some seeds develop into fruit. So when you're enjoying an apple, you're actually eating a fertilized plant ovary.

However, plants don't fertilize their ovaries so we can eat them. The purpose is to make new plants. Plants want to spread their seeds to increase reproductive success. To do this, plants use seed dispersal, or methods to spread their seeds in a large geographic area.

Types of Seed Dispersal

Different plants have different strategies to disperse seeds, depending on the environment they grow in. Here we'll go over the five main methods: gravity, force, wind, water, and animal dispersal.

Gravity and Force

Picture going to an apple orchard. As you walk through the trees, you see many apples on the ground, as well as in the trees. Seed dispersal by gravity occurs when fruits, and their seeds, fall from the tree in a process called abscission. As fruit ripens, it gets heavier, and combined with chemical signals inside the plant, the fruit falls. Some fruit may roll further from the tree, whereas others will then be carried away by other dispersal methods.

Apples use gravity as a seed dispersal method
apples

Not all plants are so passive. Some plants actually eject the seeds from their pod, much like a cannon. These plants often have seed pods that slowly dry out in the sun, creating pressure inside the pod. When the pressure is great enough, it explodes, sending seeds in all directions. Some seeds are carried even further using wind or water.

Although this might seem like a wild strategy for seed dispersal, chances are you're already familiar with some of these plants. If you take a walk through a garden in the northeastern United States, you'll probably see some shade loving plants called impatiens. When it's time to reproduce, these plants develop small, spring-loaded seed pods. When the seed pods are completely pressurized, any small disturbance, such as a touch from a human or animal, causes the pod to explode open, scattering seeds in all directions.

Impatiens seeds are dispersed by force using spring-loaded seed pods
seed pods

Wind and Water

As a child, you probably picked dandelions. When flowering, these plants have a golden yellow color. However, as the fruit ripens and the seeds are ready to disperse, the flower develops seeds with fluffy parachutes attached to them. If you pick one of these flowers and blow on it, the seeds fly everywhere, spiraling away like tiny helicopters. Dandelions use wind as their method of seed dispersal. During wind dispersal, seeds are made to fly away in the wind. This usually happens through modifications to the seed to make each one light and easily picked up by the wind, such as our dandelion. Dandelion seeds are so well evolved that they can travel hundreds of miles if the wind is strong enough, effectively spreading their seeds to colonize new habitats.

However, seed dispersal by wind can be a gamble for the plant. It's hard to know where the seeds will ultimately end up and if the conditions there will be suitable for germination. Thus, plants that use wind dispersal often make lots of seeds in hopes that at least some will find the proper habitat.

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