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Introduction to Seed Dispersal

Seed dispersal is the term coined for the movement of the seed from one place to another. This movement generally occurs with the help of dispersal vectors. Dispersal vectors can be biotic or abiotic components. Biotic dispersal vectors include animals, bees, and other insects whereas abiotic factors are wind, and water.


The need for dispersion arises because plants need to transport their seed far from the parental plant, this is done to reduce the intraspecific competition between the parent and progeny. The pattern of seed dispersion is greatly dependent on the dispersal vector that is being used. The following are the main types of dispersion mode - gravity, wind, water, animal, and animals. The dispersal unit of the plant is known as the diaspora, it includes seeds and additional tissue that assists in the seed dispersion.


Seed dispersal can be broadly classified into autochory and allochory. Autochory refers to the dispersion of the diaspore without any help from the external environment, whereas allochory refers to the dispersion of seed with the help of dispersal vectors. Ballistic and dispersion through gravity comes under the autochory mode of dispersion. Ballistic dispersion refers to the condition when a seed is ejected by the dehiscence of the fruit.


Seed Dispersal by Animals and Birds

Animals and birds disperse the seeds in different manners. Colourful fruits attract animals and birds. When they eat these fruits only the pulpy part is digested in their bodies and the seeds are excreted out by their systems in the form of their dropping, which eventually gives birth to new plants. Blackberry, cherry, tomato and apple seeds are usually dispersed in this way.


There are some species of squirrels that collect nuts from different plants like acorns and bury them under the ground as they store food for the winter season, these squirrels usually forget the place where they have previously buried the nuts and the seeds germinate into new plants.


Some plants bear seeds with hooks. A common example for such a type of plant is the Burdock plant. The seed of these plants gets attached on the fur of animals with the help of these hooks and are carried away to different places, far from their parent plants.


Examples of plants having seeds dispersed by animals are Dates, rambutan, sea grapes, sea holly, tamarind, raspberry, sunflower, tomatoes.


Dispersal by Animals

Seed dispersal by animals comes under the category of the allochory. Dispersal by the animal is termed as zoochory, zoochory. It can be further classified into saurochory, ornithochory, and, myrmecochory, which means dispersion by reptiles, birds, and ants respectively. Based on the way of carrying the diaspore zoochory can be classified as endozoochory, epizoochory, and synzoochory.


Endozoochory: 

It is the condition when seeds are carried within the dispersal vectors, which are animals in this case. It is an example of mutualism between plants and animals. In this type seed is generally inside the fruit, animals that perform dispersion eat the fruit surrounding the seed and discard the seed at a distant location, thus performing dispersion. The plant provides fruit to meet the nutritional requirements of the animal whereas the animal helps in plant survival by allowing it to grow in various locations, thus both the species mutually benefited from the seed dispersal by animals.


Epizoochory:

It is the condition when an animal carries the diaspore outside its body. This condition arises in the case of accidental dispersion of the seed by animals. When animals or birds pass by the seed some of the seed might get attached to the body of the animal and move along with it, diaspore than generally falls at a distant location from the parental plant. 



Synzoochory:

It is a condition when the diaspore seed has not completely entered the alimentary canal of animals rather they carry the seed in their mouth. Synzoochory is often seen in seed dispersal by squirrels. It is also done by rodents and birds.  Synzoochory has a characteristic feature, the seed is generally a nut that is used as a food source by the animals.


Diplochory is also considered as a type of syn zoochory where it is indirect or two-step dispersion by an animal, this occurs when the nut is the food source of more than one species. It is a highly effective way of dispersion.


Seed Dispersal by Water

In the plant kingdom, water is natural and one of the fundamental sources of seed dispersal. In this mode of seed dispersal, seeds float away from their parent plant in rivers or ponds due to their light weight. Plants which grow near water bodies usually rely on water to transport their seeds to different places. The seeds of such plants are light in weight and thus float, or there may be fluff that helps buoyancy. This method of dispersal is mainly seen in those plants which are found in water or nearby the water bodies like sea shores, lakes, ponds etc. Some examples of plants whose seeds are dispersed by the water are Coconut, palm, mangroves, water lily, and water mint.


Characteristics of Seed Dispersal by Water:

 There are some characteristic features of hydrochory they are as follows,

  1. Diaspore must be lightweight and hollow

  2. Diaspora can swim

  3. They generally have long filaments

  4. They generally do not produce nectar

  5. They are not usually very colorful

  6. They must have the property of hygrochasy, that is seed can germinate in moist weather.


Example of Seed Dispersal by Water

There are some of the following examples of water dispersal of seeds,

  1. Mangrove plants are the best example of hydrochory.

  2. Aster tripolium and Juncus species are some examples of hydrochory where seeds are transported to distant areas

  3. Mesembryanthemum, Sedum, and other plants show characteristic features of hygrochasy.

  4. Sea dispersal of the coconut palm is the best-studied common example of hydrochory.

  5. Some other examples of plants that use water for seed dispersal are water plantain, yellow flag, sea kale, sea rocket, sea beet.

 

Seed Dispersal is an adaptive mechanism that can be seen in all seed-bearing plants, it can be defined as a method by which seeds move away from their parent plant in order to germinate and survive at a different place. There are many vectors/modes of transportation of the seed from one place to another.


Types of Seed Dispersal

  • Seed Dispersal by Wind

  • Seed Dispersal by Water

  • Seed Dispersal by Animals and Birds

  • Seed Dispersal by Gravity

  • Seed Dispersal by Explosion

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FAQs on Seed Dispersal by Animals

1. Where can I find useful study resources for Dispersal of Seeds?

You can find everything you need on the Vedantu app or website. These resources are created by professionals and the content is accurate and reliable. Students can read about Seed dispersal, its types, various vectors that help in seed dispersal and a whole lot more! These study materials are free for studying and there is no cost at all. All students have to just sign in and then you will be able to download what you want in pdf format. Students can take advantage of these free resources that will surely help them ace their exams.

2. What are the various ways by which seeds are dispersed?

There are various ways by which seeds are dispersed. Two of the most fundamental means of seed dispersal are wind and water, these vectors carry light seeds to various places where they can germinate. Animals and birds also play a key role in the dispersal of seeds as they carry seeds away from their parent plant for germination. Seeds also disperse by the means of gravity and explosion in which the fruit shoots out the seed in the external environment for germination.

3. What is seed dispersal?

Seed Dispersal is a natural process, it is an adaptive mechanism that can be seen in all seed-bearing plants, it can be defined as a method by which seeds move away (or are transported away) from their parent plant in order to germinate and survive at a different place. There are many vectors/modes of transportation of the seed from one place to another. Seed dispersal is very important for the growth of new plants because if the seeds just fall on ground under the parent plant, they might not get enough sunlight, water or nutrients from the soil.

4. What are some examples of seed dispersal by water?

Some examples of dispersal of seeds by water are given below:

  • Mangrove plants are the best example of dispersal of seeds by water.

  • Examples of plants where seeds are transported to distant areas via water are Aster tripolium and Juncus species.

  • Mesembryanthemum, Sedum, and other plants show characteristic features of dispersal of seeds by water.

  • Sea dispersal of the coconut palm is the best-studied common example of seed dispersal by water

  • Some other examples of plants that use water for seed dispersal are water plantain, yellow flag, sea kale etc

5. What is seed dispersal by water?

In this mode of seed dispersal, seeds float away from their parent plant in rivers or ponds due to their light weight. Plants which grow near water bodies usually rely on water to transport their seeds to different places. The seeds of such plants are light in weight and thus float, or there may be fluff that helps buoyancy. This method of dispersal is mainly seen in those plants which are found in water or nearby the water bodies like sea shores, lakes, ponds etc. Examples of plants whose seeds are dispersed by the water are Coconut, palm, mangroves, water lily, and water mint.

6. List some examples of seed dispersal by birds.

Seed dispersal by birds comes under the category of synzoochory, where birds carry their diaspore within their beaks. Some of the examples of seed dispersal are listed below

  • Pisonia, a fruit whose seed is carried to pacific islands through birds.
  • Phoradendron, a North American plant uses birds for dispersion
  • Ameyema is also known as Australian mistletoe also uses birds for dispersion.

7. List some fruits dispersed by wind.

European pine (Pinus sylvestris), dandelion, Javan cucumber (Alsomitra macrocarpa), a tropical climber are some of the examples of fruits dispersed by wind.

8. What is diplochory?

It refers to the indirect or two-stage dispersion of seeds, it is done when there is competition for the food source as both species use the same seed as a food source.


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