Seed Dispersal: Definition, Importance, Types & Advantages

While animals can move freely from one place to another, plants have limited mobility. Then how do plants not end up at their origin? How did plants scatter their offspring in different localities and habitats? The answer to this question lies in the phenomenon of seed dispersal. Read the entire article to understand seed dispersal in detail. 

Keyterms: Seed, Reproduction, Plants, Transportation, Food, Sunlight, Water, Minerals, Autochory, Allochory, Phenomenon, Adaptation

Read More: Reproductive System Humans

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Seed Dispersal: Definition

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Seed dispersal refers to the phenomenon of seeds movement or transportation from plants to distant places. 

The destiny of the seed depends on the effectiveness of dispersal as plants cannot choose the landing place for their offspring. Seed dispersal is considered to be an example of adaptation.

The video below explains this:

Seed Dispersal Detailed Video Explanation:

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Importance of Seed Dispersal

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If all the seeds fall to the ground under the parent plant, they might not get enough resources like food, sunlight, water, and minerals to germinate and grow. Thus, seed dispersal ensures the survival of the progeny of the plant.

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Adaptive strategies of seeds for dispersal

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1. The genesis of diaspore: A diaspore is a dispersal unit of a plant that consists of spores or seeds, and additional tissues that aid seed dispersion. 
2. Modification in seed structure, composition, and size: Different seeds are modified in different ways to get transported via different agents or vectors. 

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Types of seed dispersal

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It is broadly classified into Autochory and Allochory.

Allochory

Seeds dispersal takes place with the help of external agents. It is further divided into four types.

1. Dispersal by wind (anemochory): Seeds are carried naturally by the wind from one place to another. Seeds of plants like orchids, dandelions, swan plants, and cottonwood trees are minute, light in weight, and have feathery bristles. Plants possess certain adaptive strategies as follows.

1. Winged-like appendages developed from the seed coat, pericarp, or persistent sepal provide buoyancy and help them to float. Winged seeds are commonly found in Moringa, Indian trumpet flower, Mahogany plant, Dipterocarpus, Hiptage, and Acer. 
2. Seeds of dandelion (Taraxacum) exhibit a parachute-like structure called pappus, calotropis are topped with white and silky hair tufts called the coma. Such appendages aid the suspension in air for a long time and thus seeds are transported at a great distance. 
3. Poppy seeds release slowly from the fruit through minute openings with a delicate force of the wind. This mechanism is known as the censer mechanism.
4. Ground cherries have a balloon-like modified structure that helps the fruit and seed to remain in the air for a longer period.

2. Dispersal by water (hydrochory): Seeds float away by water currents of water bodies like rivers, ponds, and the sea. The Covering of coconut has sufficient air spaces using which it can float on water to reach land and germinate. Lotus has spongy thalamus that aids in floating. Seeds of palm, mangrove, and water-lily plants are also dispersed by water.

3. Dispersal by fire: Plants like pine trees need heat to open cones and release seeds. This helps to survive seeds in case of a forest fire.

4. Dispersal by an animal (zoochory): Zoochory is further classified into endozoochory, epizoochory, and synzoochory.

1. Endozoochory: Animals eat the fruit around the seed and discard the seed at a distance. This disperses the seed in various locations.
2. Epizoochory: Seeds adhere to the body of the animal using barbs, spines, barbs, hooks, or sticky glands when they pass by and are transported along with them.
3. Synzoochory: Rodents like squirrels nibble nuts like walnuts, peanuts, acorns and carry the seeds in their mouth. Sometimes they cache and forget the seeds buried under the soil. Nuts germinate into plants. 
4. Birds like bellbirds feed on juicy parts of the fruit like apple, blueberry, tomato and excrete out undigested seeds in the form of their droppings. The color and taste of the fruit attract birds.

Autochory

Seed dispersal takes place without any help from an external agent. It is further divided into two types.

1. Dispersal by explosion- Some plants like okra and pea have pods, this pod becomes dry and stretched after ripening due to external factors like humidity, or pressure change. Under tension, it explodes and seeds are dispersed nearby.
2. Dispersal by gravity- Large ripened fruit like calabash gets heavier and falls, this is called abscission. On falling fruits break and disperse seeds on the ground.

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Seed survival

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Dispersal is not enough, survival of seeds after dispersal is also important. Seeds build the basis for agriculture thus survival and storage of seeds that can be used as food are crucial. Dormancy and dehydration of seeds are significant in this. Seed dormancy allows the seeds to overcome the unfavorable conditions for seedlings. It prevents pre-germination harvesting.

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Advantages of seed dispersion

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1. It increases the diversity and availability of plants over a large area.
2. It supports afforestation as plants grow in new places.
3. Seeds remain protected from predators as predators search for areas having accumulated seeds to save time and energy. Seed dispersal avoids seed accumulation in one place.
4. It ensures seedling mortality as seed dispersal minimizes the chances of intraspecific competition between parent plant and seed. 
5. Seeds grow in favorable conditions.

NCERT Solutions of: Class 12 Biology Chapter 1 Reproduction In Organisms

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Things to Remember

• Seed dispersal is the transportation of seeds from plants to distant places. Seed dispersal is important to eliminate competition for survival between parent plants and offspring.
• Seeds remain in a dormant state after getting detached from the parent plant. Seed dormancy helps to overcome unfavorable conditions. Unfavorable conditions here means that the conditions are not suitable for seeds to germinate and grow. Seeds build the basis for agriculture thus survival and storage of seeds that can be used as food are crucial.
• Seeds have modified structure, composition, and size to make seed dispersal possible. Like the seeds that disperse through the air are light in weight and have wing-like structures, whereas the seeds that disperse through water have air spaces using which they can float on water.
• Humans also help in seed dispersal, as they collect fruits from the plant, consume them and then dispose of the seed at some different place which is at a distance from the parent plant.

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Previous Years Questions

1. Type of asexual reproduction found in Hydra is..[KEAM]
2. Which of the following is having longitudinal binary fission ?….[KEAM]
3. In grafting, the stock and scion should be joined….
4. Banana is vegetatively propagated by… [AMUEEE 2012]
5. Vegetative propagation by leaves is seen in… [JKCET 2010]
6. Vegetative propagation in water hyacinth takes place by...[AMUEEE 2013]
7. A slender, prostrate subaerial branch of the stem which creeps along….
8.  Meiosis takes place in...[NEET 2013]
9. The sexual reproduction is absent in….[NEET 1995]
10. For union between stock and scion in grafting which one is the first to occur….[NEET 1990]
11. A clone is ......… [KCET 2011]
12. Animals which possess cleidoic eggs exhibit….[KCET 2011]
13. Which among these is not a post fertilization event ?...[KCET 2016]
14. Mode of DNA replication in E. coli is….[UP CPMT 2005] 
15. Match each function below with the associated part or parts of the human male reproductive system shown in the figure.​