Introduction

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. Although the anatomy of seeds of different plants may differ in many ways, the underlying anatomy remains the same. 

The following are the components of a typical seed:

Testa :- This is the seed’s outer coat that serves as a protective barrier for the developing plant inside. MicropyleIt’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 :- it’s a scar created by the stalk that connected the ovule to the ovary wall before it became a seed. CotyledonThis 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.

EndospermIn many plants, a distinct component called the endosperm develops for starch storage. It can be found in both maize and wheat.

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.

• The embryo of a plant is protected inside 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.

Parts Of A Seed

A seed is an important part of a flowering plant. They give rise to a new plant. They may be of different shapes, colours and sizes. They may be round, wrinkled, winged or hairy. They are in a dormant condition until they receive adequate sunlight, water, and soil. The growth of the plant from a seed is known as germination. A seed has three parts:

Seed Coat

Endosperm

Embryo

Seed Coat

A seed coat protects the internal parts of a seed. The seed coat has two layers. The outer layer is thick and known as the testa. The inner layer is thin and known as tegmen.

A thick seed coat protects the seed from sunlight and water. It prevents the loss of water and entry of parasites within the seeds. The hard seed coats prevent germination during unfavourable environmental conditions.

An opening in the integument of the ovule is known as the micropyle and is visible on some seed coats. The hilum is also visible which is equivalent to the naval in humans where the umbilical cord is attached.

Endosperm

The endosperm contains the nutrients stored in it. It provides nutrients to the seed in the form of starch, carbohydrates and proteins to support the embryo during germination. It is located below the seed coat. The seeds remain viable with the intake of nutrients until germination.

The endosperm may be mealy, continuous or ruminated. An endosperm has a triploid chromosome complement.

In corn and other cereals, endosperm constitutes a major portion of the seed. In seeds like beans, the endosperm is utilised in the embryo development and is absent in the seed. Coconut is the liquid endosperm.

Embryo

The embryo is the most important part of a seed. It is diploid, developed from the fertilised egg. All the cells that need to develop into a mature embryo are present within the embryo. An embryo comprises the following parts:

• Epicotyl
• Hypocotyl
• Radicle
• Cotyledons

Epicotyl is a small shoot which gives rise to the entire plant shoot system.

The primary root emerges first during germination. It is also known as hypocritical. It anchors the plant firmly in the soil.

Radicle is a small embryonic root.

The cotyledons provide nourishment to different parts of the embryo. It emerges as a tiny or fleshy leaf from the soil with the seedling during growth. It stores food in the form of starch and protein.

The embryonic leaves are the first to appear above the ground. An embryo develops from a fertilised egg.

Types of Seeds

There are two types of seeds:

Monocotyledonous seeds

Dicotyledonous seeds

Dicotyledonous Seed

It is a seed produced by a plant belonging to the botanical group identified as Dicotyledons. This group includes plants such as buttercups and butterbeans.  

Monocotyledonous seed

Monocotyledonous Seed is a seed produced by a plant belonging to the botanical group identified as Monocotyledons. This group includes plants such as lilies and Lychee trees.

 This is formed as the end product of sexual reproduction in plants, and this is only for angiosperms and gymnosperms. 

Gymnosperm seeds are exposed because they have no fruits or flowers. On the other hand, angiosperms have matured ovules that will develop within the fruit after fertilisation. 

This will consist of an embryo that is enclosed in a protective outer covering called the seed coat. An embryo is of three types – a radicle, an embryo axis and cotyledons. Based on the number of Cotyledons, seeds are divided into two –  Monocots (Monocotyledons) and Dicots (Dicotyledons). 

 Monocot Seeds

Monocots can have only one seed leaf in the seed coat. Most of the time it is only a thin leaf due to the fact the endosperm to feed the new plant isn’t always in the seed leaf. 

Examples of Monocot Seeds: Rice, wheat, maize, bamboo, palm, banana, ginger, onion, garlic, lilies, daffodils, iris, tulips are examples of Monocot seeds.

Characteristics of Monocot Seeds

The characteristic of monocot seeds is given bellow, 

1. Cotyledon is single with an embryo.
2. Pollen is single with the pore.
3. Parts of the flower are in multiples of three.
4. Scattered stem vascular bundles.
5. Adventitious roots. 
6. Lack of secondary growth.  

Structure of Seed Monocot

Embryos of monocot seeds have one massive cotyledon, and that’s known as scutellum. This scutellum is shield-shaped and is placed closer to the side of the embryo axis.

 In monocot seeds, the endosperm is covered from a proteinous layer known as aleurone layer. The embryo axis of monocots is of shoot tip; they are enclosed in a sheath known as coleoptile and a root tip radicle that is enclosed in coleorhiza.

Most of the monocot seeds are thick, swollen endosperms for nourishment. They also are referred to as albuminous. 

During the embryo development, the endosperms aren’t totally developed, and it is the nourishing tissues in seeds.

Dicot Seeds

Dicot seeds (Dicotyledons) are the seeds that have  embryonic leaves and cotyledons. They are one of the  groups into which all of the flowering plant life has been divided. 

Examples of Dicot Seeds:

Bitter gourd seeds, Castor seeds, Mango seeds, Neem Seeds, Night Jasmine seeds, Papaya seeds and Tamarind seeds. 

Characteristics of Dicot seeds: 

1. It consists of  cotyledons.
2. The outer overlaying of dicot seed is the seed coat, which has  layers known as outer testa and inner tegmen.
3. The embryo remains inside the seed coat and consists of an embryonic axis and  cotyledons. 
4. These cotyledons are generally fleshy and complete of reserve meals materials. 

Structure of Dicot Seeds

Dicots also are called Dicotyledons. All the flowering plant life or angiosperms are divided into groups. Approximately 2,00,00 species of cotyledons were discovered. 

In dicots, the embryo may have an embryo axis and  cotyledons. The look of cotyledons is swollen as they maintain the meals for growing seedlings. 

There are  ends for the embryo axis. The formation of the shoot tip is referred to as plumule and the root tip on the lower end is referred to as the radicle. 

This content material is covered with a protective coat referred to as seed coat that is made up of Testa and Tegmen.

Conclusion

All the flowering plants or angiosperms are divided into groups. So far there are about 2,00,00 species of cotyledons have been discovered. In dicots, the embryo will have an embryo axis and two cotyledons. The appearance of cotyledons is swollen as they preserve the food for developing seedlings. There are two ends for the embryo axis. The formation of the shoot tip is called plumule and the root tip at the lower end is called the radicle. This content is covered with a protective coat called seed coat which is made up of testa and tegmen.