Development of Seed and Fruit Formation: On a hot day, many of us enjoy a cool slice of watermelon, and in the fall, many of us have gone apple picking. Bananas are the most popular fruit in the world, and avocados contain more fat than any other fruit or vegetable on earth. But what exactly are fruits? And where do they originate? We’ll have a look at the answers to these questions on the Development of Seed and Fruit Formation.

Plants produce seeds and fruits as a result of fertilisation or sexual reproduction. In angiosperms, the ovary develops into the fruit, while the ovules develop into the seeds encased within the fruit. Gymnosperms and angiosperms both produce seeds. Let us learn about the development of seeds and fruit formation, structure, types, and significance of seed and fruit formation.

What is a Seed?

A  seed is a fertilised mature ovule with an embryonic plant, food reserves, and one or more protective coats. Seed is the reproductive structure that all phanerogams have in common. Although there may be variations in the shape or size of the seed or the relative proportion of various parts, they are always built on the same plant.

Seeds come in a wide range of sizes, shapes, colours, and surfaces. The seeds range in size from small dust particles to huge double-coconuts, as found in some orchids. During unfavourable climatic conditions, the seeds do not germinate and go into a period of suspended growth or rest. Once favourable conditions return, the seed resumes metabolic activities and grows into a full plant. A plant in the form of seeds can be transported over vast distances without any additional precautions. Fruits are produced when the ovary develops into fruit after fertilization, and thus fruit is also referred to as a ripened ovary. We’ll look at how the formation of the seed occurs in this article.

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Seed Formation

1. The fertilized ovule develops into a seed. It can store reserve food materials and, in favourable climatic conditions, can grow into a new plant.
2. Fertilization is the process of a zygote being formed by the union of male and female gametes. Water, wind, butterflies, insects, animals, birds, and other pollination agents transfer pollen grains to the stigma.
3. As a result of fertilisation, the zygote divides and develops into an embryo, the primary endosperm nucleus gives rise to endosperm, and the protective coats are formed from integuments. Except for the ovary, every part of the flower loses after fertilisation.
4. The development of seeds is the final step in the reproduction process in plants.
5. The emerging embryo develops and matures within the seed.
6. The seed thus has a basic structure of an ovule with some parts lost and some new ones developed.
7. The seed remains attached to the placenta through a small stalk-like structure called a funicle, a place of detachment from the funicle that appears as a scar called hilum.
8. In some seeds, a bright coloured structure develops on the surface as an outgrowth called an aril; when it occurs as an outgrowth of a funicle, it’s called strophioles.

Classification of Seeds

Factor	Classification	Examples
On the basis of the number of cotyledons present	• Dicotyledonous Seeds • Monocotyledonous Seeds	• Gram, bean • Rice, maize
On the basis of the presence or absence of endosperm	• Albuminous (Endospermic) • Exalbuminous (non-endospermic)	• Mango, Orchids • Castor, Cereals

Fig: Structure of Seed

Structure of Seed

A seed is generally made up of a seed coat and embryo.

(a) Seed Coat: It is the protective covering of the seed derived from one or both integuments of the ovule. Usually, the seed coat is two-layered. The outer thick and hard layer is called testa, while the thin inner membranous layer is called tegmen. The exterior of a seed coat contains prominent structures like hilum, raphe, micropyle, and chalaza.

(b) Embryo: It represents the dormant future plant that remains enclosed within the seed coat. The embryo consists of an embryo axis or tigellum and cotyledons. The embryo axis consists of plumule, epicotyl, cotyledonary node, hypocotyl, and radicle. Plumule represents the embryonic shoot, while radicle represents embryonic root. The embryo axis has a node called the cotyledonary node that bears one or two cotyledons (= seed leaves). The part of the embryo axis between the plumule and the cotyledonary node is called epicotyl, and a similar region between the cotyledonary node and the radicle is called the hypocotyl. The seed contains reserve food either in cotyledons or in a special tissue called endosperms.

Difference between Monocotyledonous and Dicotyledonous Seeds

Monocotyledonous Seeds	Dicotyledonous Seeds
The seed contains a single cotyledon.	The seed possesses two cotyledons.
The food is commonly stored inside the endosperm (exception-orchids).	The food may be stored inside endosperm or cotyledons.
An aleurone layer of special protein-rich cells is found on the outside of the endosperm.	This layer is absent.
Special sheaths, coleoptile over plumule and coleorhiza over radicle, may be found on the embryo tips.	Coleoptile and coleorhiza are absent.
Embryo occupies one side of the seed.	The embryo takes up the entire interior of the seed or just the central portion.
Plumule lies at one end near the cotyledon.	Plumule lies in between the two cotyledons.

What is a Fruit?

The fruit is a mature or ripened ovary; after fertilisation. A parthenocarpic fruit is one that develops without the ovary being fertilised. True fruits are those that develop from the ovary, whereas accessory fruits are those that develop from other regions of the female gametophyte. The fruit comprises a wall or pericarp and seeds. The pericarp might be fleshy or dry. The outside epicarp, middle mesocarp, and inner endocarp are formed when the pericarp is thick and fleshy. But in dry fruits, the pericarp is undifferentiated and is papery or woody. They are high in nutrients, and some, like tomatoes, can also be consumed as vegetables. Fruit pericarps are further subdivided into:

Fig: Fruit pericarp and seed layers

1. Exocarp-This is the outermost layer of the epidermis, which is generated from the outer layer.
2. Mesocarp– This is the second or middle layer of the fruit, which is usually juicy and varies in thickness depending on the fruit.
3. Endocarp– This is the innermost layer of the fruit, and it varies depending on the type of fruit.

Development of a Fruit

As the zygote is created after pollination and fertilisation, and the ovary begins to develop into the fruit. The pericarp develops as the ovary’s exterior wall differentiates while the seed grows within the fruit itself. When a fruit develops exclusively from the ovary, it is said to be True fruit. This type of fruit contains no other floral parts. E.g.: Mango, Guava, grapes, etc. False Fruits are made up of the ripened ovary and other floral parts such as the base or receptacle, thalamus, the perianth, and so on. E.g., Apple, pear, etc.

Fig: True and False Fruits

Classification of Fruits

There are three main types of fruits:
1. Simple fruits
2. Aggregate fruits
3. Composite fruits

1. Simple Fruits: These fruits are made up of only one carpel or more than one carpel of a flower with or without the participation of accessory parts. Based on the type of their pericarp and layers, they are further categorised into Fleshy and Dry fruits.

Fig: Fleshy Fruits and Dry fruits

I. Fleshy Fruits

The pericarp of fleshy fruits is fleshy and juicy, as the name implies. They also come in a variety of shapes and sizes:
1. Drupe– The exocarp is thin, the mesocarp is thick and juicy, and the endocarp is rocky in this form of a simple fleshy fruit. Mango, plum, and coconut are examples of such fruits. The endocarp is lacking in this form of fleshy fruit, and the seeds are distributed throughout the mesocarp. Grapes, bananas, and tomatoes are just a few examples.
2. Pome– Because the thalamus is a part of the fruit, it is a fake fruit. Apples and pears are examples of this type of fruit.
3. Berry– A berry is a fleshy fruit with no stone (pit) that develops from a single flower with one ovary. Grapes, currants, and tomatoes, as well as cucumbers, eggplants (aubergines), and bananas, are considered berries under this classification but exclude certain fruits that meet the culinary definition of berries, such as strawberries and raspberries.
4. Pepo– It is a fleshy, several-seeded fruit that has developed from one flower having a single ovary divided into several carpels, which develops a firm or tough rind as it matures (such as melon, squash, cucumber).
5. Hesperidium– It is a modified berry that has been transformed by a single ovary. The fruit is made up of 8–16 carpels, which constitute the fruit’s core or segments, which contain the seeds and juice. Example- Orange, lemon.

II. Dry fruits

There are two sorts of dry fruits: those with juicy or thick pericarps and those without pericarp.
Dehiscent Dry fruits
If the pericarp bursts open at maturity and release the seeds, they are dehiscent fruits. They come in a variety of shapes and sizes:
1. Follicle– These fruits are made up of a single carpel and only dehisce along a single suture or edge. Calotropis, for example.
2. Legume– These fruits are made up of a single carpel that splits along both sutures. Beans, for example, are legumes.
3. Capsule– A capsule is made up of several carpels. It has numerous pores or chambers, and as it dehisces, it splits into many pieces, releasing seeds. Lady’s Finger is a good example.
4. Siliqua-It is made up of two carpels that dehisce from the base upwards, the seeds remaining attached to the base. For instance, mustard.
5. Silicula- A short and broad siliqua containing only a few seeds. E.g., Shepherd’s purse.

Indehiscent Dry Fruits or Achenial Fruits

These fruits do not dehisce or burst to release the seeds. They are of many types:
1. Achenes: They have a single seed coat that is distinct from the fruit coat or pericarp. Magnolia, for example.
2. Caryopsis: It is similar to achene, but the seed coat and the fruit coat are fused together. Maize Samara, for example, is a single-seeded fruit with wings. Hiptage and Ash are two examples.
3. Nut: A hard pericarp surrounds a single-seeded fruit. It could also have a husk on one of its walls. Oak and chestnut are two examples.
4. Cypsela: A bicarpellary inferior pistil gives rise to a cypsela. It’s a dried single-seeded fruit produced from a double ovary of which the only one matures into a seed—for example, sunflowers.
5. Schizocarpic: It is a subtype of indehiscent fruits that consists of two carpels that separate along the midline at maturity into two one-seeded halves, each indehiscent. This fruit is developed from the syncarpous pistil—for example, Mimosa, maple, coriander, and hollyhock.

2. Aggregate Fruits
These fruits are made up of a cluster or aggregate of numerous distinct pistils borne on a single flower. Etaerio is a term used to describe a collection of fruits that emerge from a single bloom. The aggregate fruits are of the following types.
1. Etaerio of drupes- Eg: Raspberry
2. Etaerio of achenes- Eg: Strawberry
3. Etaerio of follicles- Eg: Magnolia
4. Etaerio of berries- Eg: Custard apple

3. Multiple Fruits or Composite Fruit
Multiple fruits refer to when a complete inflorescence matures into a single fruit. Pineapple, figs, mulberry, and jackfruit are other examples. Composite fruits are of two types:
i. Sorosis: They develop from catkin, spikes, and spadix type of inflorescence. Eg: mulberry, jackfruits, and pineapple.
ii. Syconus: This develops from hypanthodium type of inflorescence.

Pomology

Pomology is the science of growing fruit and nuts, and it is the study of fruit. Pomology was first introduced in the United States in 1886 when the USDA established a pomology section. Charles Downing, an American pomologist, is referred to as the “Father of Pomology.”

1. Development, enhancement, cultivation, and physiological studies of fruit trees are the core topics of pomological research.
2. Fruit tree improvement aims to improve fruit quality while also regulating production periods and lowering production costs.

Parthenocarpy

The process of growing or developing fruits without pollination and fertilisation is known as parthenocarpy. Parthenocarpy can be found in two forms: naturally occurring and artificially produced. Eg: Grapes, Lemon Tomato, and Watermelon

Differences Between Seed and Fruit

Seed	Fruit
Fertilized ovule	Fertilized ovary
Through a funicle connected to the placenta	Through a stalk attached to a branch
One scar called the hilum	Two scars (style scar and stalk scar)
Has seed coat/testa	Has fruit wall/pericarp
Seed wall undifferentiated	Fruit wall is differentiated

Significance of Seed Formation

The significance of seed formation is as follows:
1. Seed formation is a more dependable method, firstly, since reproductive processes such as pollination and fertilisation are independent of water. Seeds need a high rate of metabolism that further needs enzymatic activity, and enzymatic action needs water.
2. Seeds provide a protective layer for the embryo plant, allowing it to develop once it finds suitable soil.
3. Seeds are a protective structure that allows a plant embryo to remain metabolically inactive before germinating. The seed can remain dormant until the embryo’s growth conditions are favourable.
4. Food sources for plant embryos are pre-packaged in seeds to meet the demands of embryos in their early stages of development.
5. Animals, wind, birds, and other agents may quickly transport seeds, allowing the plant to populate a broad region. Some are even so light that powerful winds can carry them across the globe.
6. The seeds are dry and have a latent embryo protected by a thick seed coat. As a result, it is suitable for presentation in adverse situations.
7. Seeds have the potential to disperse and colonise new habitats.
8. Sexual reproduction is used to create seeds. As a result, they have various variants that enable them to adapt to various environmental situations.

Significance of Fruit Formation

The significance of fruit formation is as follows:
1. The seeds are protected by the developing fruits from bad weather, mechanical damage, and pests.
2. Fruits, both fleshy and dry fruits, help in the dispersal of seeds to new areas.
3. Many compounds, including carbohydrates, protein oil, organic acids, vitamins, and minerals, are found in this plant. Provide nutrients to the seedlings as they grow.
4. Some fruits also aid in the development and germination of seeds.
5. Fruits are a good source of vitamins, minerals, organic acids, proteins, oil, and sugar.

Summary

The seed is a fertilized mature ovule and based on the number of cotyledons present, seeds are classified into dicotyledonous and monocotyledonous seeds.  Seed coats, cotyledons, and an embryo axis are the most common components of a seed. The embryo’s cotyledons are simple structures that are often thick and swollen due to the storage of food reserves (as in legumes).

Mature seeds may be non-albuminous or albuminous. The flower’s ovary normally develops into the fruit after fertilisation. A ripened ovary is referred to as a “fruit” in botany. True fruits are those that develop from the ovary, whereas accessory fruits are those that develop from other regions of the female gametophyte. The seeds and developing embryos are protected by the fruit, which encloses them.

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Frequently Asked Question (FAQs) on Development of Seed and Fruit Formation

Q.1. How do seeds and fruits develop?
Ans: Plants produce seeds and fruits as a result of fertilisation or sexual reproduction. In angiosperms, the ovary develops into the fruit, while the ovules develop into the seeds that are encased within the fruit. Gymnosperms and angiosperms both produce seeds.

Q.2. What is the advantage of seed formation?
Ans: The seed contains the future plant or embryo that develops into a seedling, which is one of the advantages of seed development. Seeds can be transported by wind or animals into new locations, allowing the species to expand to new territory while also preventing extinction.

Q.3. What is the difference between fruit and seed?
Ans: The main distinction between fruit and seed is that fruit is an angiosperm’s formed ovary following fertilisation, whereas seed is a plant’s fertilised ovule.

Q.4. What is the significance of seed and fruit formation?
Ans: Fruits supply nutrients to the seeds as they grow. In immature conditions, fruits protect the seeds. Plant seeds are key propagation organs (units). Seeds and fruits acquire specific devices for dispersal, which help in the species’ dissemination.

Q.5. What are the 3 types of fruit?
Ans: Based on the number of ovaries and the number of flowers involved in the fruit formation, fruits are classified into three major groups namely:—simple fruit, aggregate fruit, multiple or composite fruits.

Now you are provided with all the necessary information on the development and seed formation and we hope this detailed article is helpful to you. If you have any queries regarding this article, please ping us through the comment section below and we will get back to you as soon as possible.