How are Seeds Formed?
The seed is the part of a plant that grows from the ovules after fertilisation. They're contained within the fruit that grows from the fertilised ovary.
Sexual reproduction produces seeds, which contain a young embryo capable of growing into a new plant.
Structure of a Seed
Although the anatomy of seeds from different plants may differ in many ways, the underlying anatomy remains the same. The following are the components of a typical seed:
Tesla
This is the seed's outer coat that serves as a protective barrier for the developing plant inside.
Micropyle
It's a little pore in the testa that's located on the opposite side of the radical's tip. Before active germination, it allows water to enter the embryo.
Hilum
A hilum is a scar created by the stalk that connected the ovule to the ovary wall before it became a seed.
Cotyledon
This includes a lot of starch and serves as a food supply for the developing embryo before germination in some plants; in other plants, and endosperm serves in this role. There is just one cotyledon in monocotyledons, but there are two in dicotyledons.
The cotyledons may remain underground or be dragged above the earth, depending on the kind of germination (epigeous or hypogeous).
Radicle
The embryonic root will eventually develop into the plant's major root. During germination, it is usually the first component of the embryo to emerge from the seed.
Plumule
The embryonic shoot is known as a plumule. It appears as a bud that will give rise to the shoot and the rest of the plant's structures.
Endosperm
In many plants, a distinct component called the endosperm develops for starch storage. It can be found in both maize and wheat.
Function of Seed
The following functions are carried out by the seeds:
They aid in the germination of new plants.
Food reservoirs in the form of cotyledons and endosperm are found in the seeds.
The embryo inside is protected by the seed coat, which is protective.
Importance
The embryo plant is protected by seeds, which allows it to develop once it finds adequate soil.
Seeds are a protective structure that allows a plant embryo to live for a long time before germinating.
Until the embryo's growing conditions are favourable, the seed can remain dormant.
To address the needs of embryos in their early stages of development, food sources for plant embryos are pre-packaged in seeds.
Creatures, wind, birds, and other animals may quickly transport seeds, allowing the plant to populate a broad region. The wind can carry some of them anywhere.
Seeds can survive without water, thus the plant can survive if there is a drought.
Seeds are produced in vast quantities so that plants can reproduce.
FAQs on Seed Formation
1. What is Fertilisation?
Seed formation begins with the combination of a male and female gamete: a process known as fertilisation. Fertilisation, occur when both male and female gametophytes are fully mature. This usually occurs in a dual fusion process known as double fertilisation. When the pollen grain deposit on the stigma, it germinates by building a pollen tube, which grows down the style, through the micropyle and into the embryo sac, with the tube nucleus following the tube apex downwards. The tube nucleus breaks, but the two pollen sperm cells enter the embryo sac, one fusing with the diploid polar nucleus to form a triploid endosperm nucleus and the other fusing with the egg cell to form a diploid zygote or fertilised egg.
2. What are Gametes?
The sex cells of plants are known as gametes. Plants have sperms and egg cells that are needed to fuse to produce a zygote to create a new plant. The plant ovary produces a female egg cell. The male sperm cell is encased in a pollen grain. Plants have two meiotic divisions- haploid cells from male and haploid cells from female – they form a diploid for the new plant. In flowering plants, the male gamete inside the pollen grain is located on the anther. Male gametes in the anther are large nucleus-containing cells. These cells go through meiotic division, forming tetrads, bundles of gametes- they become pollen grains.
3. What is Dispersion of Seeds?
The spreading or movement of seeds from one location to another using a dispersing agent is known as dispersion. The dispersion can happen through:
Wind
Wind spread seeds are often light and small enough to be easily transported away by the wind. Eg. Cotton seeds
Water
Usually, there are hollow seeds that get dispersed by water. They float on water easily and germinate once they reach a suitable location. Eg. Mangroves.
Animals
The seeds featuring spines or hooks that allow them to cling generally gets stuck to animals and spread. These seeds, like their fruits, are lovely. Eg. Guava seeds, dates.
Explosion
Following ripening, some plants toss or throw their seeds. The pods' water evaporates, causing this explosion. The seeds are moved by the wind or gravity to other sites where they grow. Eg. Viola
4. What are the stages of the Plant Life cycle?
There are 5 stages:
Seed
Seeds are similar to babies. Seeds contain the plant's embryo as well as vital sustenance and a protective shell.
Germination
The seed germinates when the soil conditions are just right. It begins by breaking through the outer shell and forming its first roots and leaves.
Growing to Maturity
The seedling will continue to develop until it is fully mature. During its development, the plant requires a variety of essential elements.
Flowering, Pollinating and seeding
When plants reach maturity, they begin to produce blooms.
Seed Dispersion
After producing seeds, plants must find a mechanism to spread them to suitable locations where they can germinate and begin their life cycle.
5. What are the requirements of the seeds to germinate?
Viable seeds are living things. To germinate, they must contain living, healthy embryonic tissue. All fully grown seeds are encased in a seed coat and contain an embryo and, in most plant species, a store of food reserves.
When soil moisture and temperature conditions are ideal for seed growth, seeds "wake up" and germinate. Too much or too little heat can damage or put seedlings into a state of rest.
For seeds to start growing inside, they need a certain amount of moisture. Seeds, like any other living entity, breathe. They require oxygen and emit carbon dioxide (CO2).
6. What are the steps of seed germination?
Imbibition. The seed coat swells and softens as it absorbs water quickly. Consider a soaked pea seed: the outer seed coat gets mushy and wrinkled as the water evaporates.
The interim or lag phase is a period between two events. During this phase, the seed's internal physiology is activated, cells respire, and the seed begins to produce proteins and utilise its food reserves.
The emergence of the radicle and the root. The cells begin to elongate and divide, allowing the seed's root and radicle to emerge.
7. Does seed germinate faster in the dark?
Some hormones send down the stem from the tip. They slow down the growth of the stem. Darkness doesn't stop the growth of stems.
Seeds that are grown in the dark use the chemical energy stored in their cells (lipids, proteins, and carbohydrates) to grow and produce more seeds.
The seeds in the light-grown condition only use some of the chemical energy they have stored up. As their chloroplasts grow, they start to use the sun's energy as well.
It doesn't matter if the light-grown seeds don't get taller than the dark-grown seeds. They have more leaves, stronger cell walls, and won't be flimsy like the dark-grown plants.
