Seed Dispersal – Definition, Advantages & Significance

Seed Dispersal: Seeds are the reproductive unit of a blooming plant capable of growing into a single plant. Seeds are also utilised as food in some plant species, such as walnuts, groundnuts, and chickpeas. The embryo, endosperm, and seed coat are the three main components of a fully formed and mature seed. The plumule is found in the seed embryo, which eventually becomes a new plant.

Have you ever wondered how seeds travel from one place to another? How does the seed dispersal take place? Do seeds have legs to walk? No, seed dispersal takes place through many agents like wind, water, human beings, animals, birds, etc. So let’s explore more about seed dispersal in the given below article.

What are Seeds?

A seed is a mature ovule after fertilization. It contains a baby plant and some food stored for the growth of the baby plant. Technically, a seed consists of an embryo one or two cotyledons and a seed coat.

1. The embryo consists of a tiny root-like structure called the radicle and a small shoot-like structure called the plumule.
2. The cotyledons mainly store reserve food material for the developing embryo. Example: gram, bean, pea, groundnut, etc.
3. In some seeds, the cotyledons are slim and do not stock food. The food is stored in a tissue or a material called the endosperm. Example: maize, rice, wheat, castor.
4. On germination, the radicle grows into the root system, and the plumule grows into the shoot system of the new plant.

What is Seed Dispersal?

The moving of seeds from the parent or mother plant to different places is called “Seed dispersal”. Seed dispersal permits the growth of identical kinds of plants in different regions. Seed dispersal is helpful because it decreases the competition for food, sunlight, water and minerals among the plants of the identical kind in the same zone. It also allows them to grow in various habitats.

Fig: Seed Dispersal

Why Seed Dispersal is Important?

Plants do not move from one place to another place. So, all the seeds produced by a plant are likely to fall underneath or very close to the parent plant. If all of them germinate, it will lead to an overcrowding of young plants. The young plants will not get enough sunlight, water and nutrients required for their proper growth. Therefore, most of them would die in their early life. To overcome this situation, the seeds and fruits have developed various devices which help them to be carried away to far off places so that they have a better chance of survival.

Types of Seed Dispersal

Depending on the seed dispersal, they are categorized into two types:

(a) Autochory: Autochory deals with  agents of seed dispersal by two types:
1. By Gravity
2. By Explosion/Force

(b) Allochory: Allochory deals with agents of seed dispersal by listed types mentioned below:
1. Wind
2. Water
3. Animals
4. Humans

1. Dispersal of Seed by Gravity: Gravity is a force of attraction that exists among all the objects and materials in the universe. As the fruits from the tree fall on the earth due to the force of attraction, they sometimes travel down to some smaller distance, get covered in the soil after a few days and germinate into a new plant. Apples, Commelina, canna, coconuts, calabash, and passion fruit are a few examples of plants whose seeds are dispersed by gravity.

2. Explosive Mechanism: The seed dispersal by force is called Ballochory. Some fruits like those of balsam and some legumes burst with a sudden jerk, and the seeds are thrown out with force in all directions. This is called an explosive mechanism for dispersal.

Fig: Seed Dispersal by Explosive Mechanism

3. Seed Dispersal by Fire: Some seeds can not escape far-off from a fire. Therefore, some plants have progressed a way to help their seeds survive. There are some classifications of pine trees that require the heat from a fire before their cones open and release seeds. Eucalyptus is another example of this.

4. Seed Dispersal by Wind (Anemochory): The seed dispersal by wind is known as anemochory. The fruits and seeds dispersed by wind are very small or very light. They possess certain adaptations.
(a) Wings: Fruits and seeds of many plants develop one or more wing-like structures, which help them to be easily carried away too long distances by air. Example: Winged fruit of hiptage, maple and winged seeds of drumstick, pine, etc.
(b) Hairs: Some seeds have a coating of hair or tufts of hair which help them to be carried away too long distances by wind—for example seeds of milkweed (Madar), dandelion and cotton.

Fig: Seed Dispersal by Wind

5. Seed Dispersal by Water (Hydrochory): The seed dispersal by water is called hydrochory. The seeds of plants that grow in or near flowing water are normally dispersed by water. Common examples are coconut and lotus. These fruits and seeds have some adaptations for floating in the water. The fruit of coconut has light and fibrous fruit walls and is carried away by seawater to long distances. Lotus has flat and spongy thalamus containing seeds. The Kowhai trees and Mangrove trees lie on the banks of rivers or estuaries; hence, seed floats on the surface of the water and water currents carry the seeds away.

Fig: Seed Dispersal by Water

6. Seed Dispersal by Animals and Birds: Seed dispersal by animals is known as zoochory. Human beings and animals eat fruits and throw away their seeds. Few fruits and seeds are either edible or develop hooks or thorns. Fleshy and edible fruits like mango, orange, papaya, watermelon, etc., are eaten by man and animals, and the seeds are thrown away, thus dispersing them.
a. Succulent Fruits: Fruits attract animals because they are brightly coloured, juicy and nutritious. When eaten, the seed passes through the animal’s faeces, which may be a long way from the parent plant.
b. Hooked Fruits: Fruits like those of cocklebur (Xanthium) and seeds like tiger-nail (martynia) have curved hooks or spines that stick to the fur of animals or to the clothing of men and are transported to distant places.

Fig: Seed Dispersal by Animals

c. Birds often swallow some seeds, which come out undigested in their droppings. In this way, birds also aid in the dispersal of seeds.

Fig: Seed Dispersal by Birds

Advantages of Seed Dispersal

1. The chances of seed survival are high because of less competition among the same species.
2. The seeds can germinate when they get favourable conditions.
3. The seed dispersal main advantage is to protect themselves from predators.
4. We can find varieties of species in one particular area.

Summary

Seed dispersal is one of the most important steps in the regeneration of a plant culture or a group of people. It identifies the prospective region for recruiting while also serving as a blueprint for the plant’s later stages of development. Seed dispersal is an adaptation process found in all seed-bearing plants that help to ensure the germination and survival of certain seeds in adult plants by moving or transporting seeds away from their parent plant. Many vectors exist to carry the seed from one location to another.

We see many fruits and their seeds around us. Every seed has got their own texture, shape, size, etc. The movement of seed from one place to another or away from the mother plant through different agents like water, wind, animals, birds, etc., is called seed dispersal. Seed dispersal is very important because it minimizes the competition for food, sunlight, water and minerals among the plants of the same kind in the same area. It also allows them to grow in different habitats. The seeds that are small and very light in weight are easily carried by the wind for miles. The seeds of plants that grow in or near flowing water are mainly dispersed by water. Many seeds get dispersed by sticking to the fur of the animals. The main advantage of seed dispersal is to escape from density-or distance-dependent seed and seedling mortality.

Frequently Asked Questions (FAQs) on Seed Dispersal

Q.1: How are seeds dispersed?
Ans: Seeds are dispersed in many ways like wind, water, animals, humans, birds; some seed pods are dispersed by the explosion method.

Q.2: What is seed dispersal?
Ans: Scattering of seeds by various methods away from the parent plant is called seed dispersal.

Q.3: How do plants benefit from seed dispersal?
Ans: Seed dispersal is helpful because it decreases the competition for food, sunlight, water and minerals among the plants of the identical kind in the same area. It also allows them to grow in different habitats.

Q.4: Which seed is dispersed by water?
Ans: Coconuts and lotus are the best examples of seed dispersal by water.

Q.5: What are the advantages of seed dispersal?
Ans: The advantages of seed dispersal are:

1. The chances of seed survival are high because of less competition among the same species.
2. The seeds can germinate when they get favourable conditions.
3. The seed dispersal main advantage is to protect themselves from predators.

We hope this detailed article on Seed Dispersal helps you in your preparation. If you get stuck do let us know in the comments section below and we will get back to you at the earliest.