Seed Formation and Seed Dispersal: Structure, Function and Importance

Introduction To Seed Formation And Dispersal

Seeds are mature ovules that contain an embryonic plant together with a nutrition supply, all enclosed by a seed coat. They are responsible for plant propagation and thus support the continuation of the species and propagation of genetic material. The seeds of plants provide survival during unfavorable times and germinate at the most opportune time.

Seed formation and dispersal are therefore important in ecological balance and maintenance of biodiversity. Seeds guarantee the survival of the plant species by making possible colonization in new areas and adaptation to new environments. Seeds in agriculture are vital for the production of crops for food security, hence offering human beings and animals a reliable source of food. Good seed dispersal mechanisms also drive the enhancement of genetic diversity in plant populations in their resilience and adaptability to natural ecosystems.

Also Read:

• Angiosperm - Life Cycle a Flowering Plant

• Events in the Germination of Pollen Grains

• Significant Differences between Anther and Stigma

Seed Formation

Seed formation is a key part of how Sexual Reproduction in Flowering Plants is done. It begins with fertilisation, where the male and female parts of a flower come together to form a zygote. This zygote later develops into a seed that can grow into a new plant. The details are given below:

Structure Of A Flower

A flower comprises the main parts: the stamen, which is the male reproductive part that consists of a bilobed anther and a filament, and the pistil, the female part consisting of stigma, style, and ovary. There is also an ovule with an egg cell. There are also petals and sepals, which protect and attract pollinators.

Process Of Fertilisation

Fertilisation happens when pollen reaches the stigma. In angiosperms, this is followed by double fertilisation. One sperm cell joins with the egg to form a zygote. The other sperm cell combines with two other nuclei to form the endosperm, which feeds the growing embryo.

Development Of Seed

The zygote develops into an embryo, accompanied by cotyledon and protective seed coat formation around. This forms a mature seed, ready for dispersal and seed germination when conditions are right.

Types Of Seeds

Monocots have one cotyledon and parallel veins, while dicots have two cotyledons and net veins. Structurally, these differences, in most cases, affect the development of plants. There are broadly two kinds Dicotyledonous and Monocotyledonous Seeds. They are mainly classified based on the number of cotyledons present.

Seed Dispersal

Seed dispersal spreads the seeds away from the parent plant, thereby reducing the competition among them and helping the colonization of new areas, thus serving diversity and survival.

Methods Of Seed Dispersal

• By Wind: Seeds are carried by the wind having adaptations such as wings.

• By Water: Floating seeds are dispersed by water bodies.

• By Animals: Seeds ingested or sticking to the fur are spread far and wide.

• By Explosion: Seeds are forcefully thrown out from the fruit.

• By Gravity (Barochory): Seeds fall to the ground due to gravity, often close to the parent plant.

MCQs on Seed Formation And Dispersal

Question 1: Seed is

1. Fertilized embryo

2. Fertilized ovary

3. Fertilized fruit

4. Fertilized Ovule

Answer: The Fertilized Ovule is the seed. Ovules convert into seeds. The fertilized ovule develops into a seed following the process of fertilization in plants. The zygote within the ovule grows into an embryo, while the ovule's integuments form the seed coat. The seed contains stored nutrients in the form of endosperm or cotyledons, supporting the growth of the embryo during germination. The ovary surrounding the ovule matures into a fruit, protecting the seed and aiding in its dispersal. Seeds are crucial for reproduction and propagation in plants, ensuring the survival of the species.

Hence, the correct answer is option 4) Fertilized Ovule

Question 2: Statement 1: Dispersal of seeds by air is called anemochory

Statement 2: Dispersal of seed by water is called hydrochory

1. 1 - correct, 2 - incorrect

2. 1 - incorrect , 2 - correct

3. 1- correct , 2- correct

4. Both are incorrect

Answer: Dispersal of seeds by different mediums - The dispersal of seeds by air is called anemochory Dispersal of seed by water is called Hydrochory. Hydrochory is water dispersal, where buoyant seeds float on water, like coconuts. Zoocory involves animals dispersing seeds either externally, by attachment to fur, or internally, by consumption and excretion. Autocory is self-dispersal, where seeds are ejected from the plant. Barochory is gravity dispersal, where seeds fall from the plant. These methods help plants spread, reduce competition, and adapt to new environments.

Hence, the correct answer is option 3) 1- correct, 2- correct

Question 3: Seeds develop after _____ from the _____.

1. Fertilization; ovary

2. Triple fusion; ovule

3. Fertilization; ovule

4. None of these

Answer: Seeds develop after fertilization from the ovule. Seeds develop after fertilization from the ovule, which contains the embryo and stored food. The outer integuments of the ovule form the seed coat, providing protection. Seeds serve as a vital means of reproduction and dispersal in angiosperms. They can remain dormant under unfavourable conditions, ensuring the survival of the species.

Hence, the correct answer is option 3) Fertilization; ovule.

Other Useful Resources:

Recommended video on "Seed Formation and Seed Dispersal"