The seeds and fruits are the results of fertilization or sexual reproduction in plants. The ovary in angiosperms develops into the fruit whereas the ovules become the seeds enclosed within the fruit. Seeds are found both in gymnosperms and angiosperms. Let us individually learn about seeds and fruits.
One of the many healthy things available in the world today is fruits. They are mostly sweet to taste, are filled with nutrients and some of them are like tomatoes are also eaten as vegetables. The fruit is broadly divided into the pericarp which is the various covering layers of the fruit and the seed or seeds which are present inside it. The pericarp of a fruit can be further divided into:
- Exocarp– It is the outermost layer which is formed from the outer layer or the epidermis
- Mesocarp– Is the second or the middle layer which is often juicy and varies in thickness in different fruits
- Endocarp– It is the innermost layer and also is different in different kinds of fruits
Browse more Topics under Sexual Reproduction In Flowering Plants
- Endosperm Development
- Fertilization and Post Fertilization Events
- Gametogenesis in Plants
- Morphology of Flower
- Outbreeding Devices and Pollen Pistil Interaction
- Parthenocarpy and Apomixis
- Sexual Reproduction
Development of a Fruit
As mentioned earlier, once pollination and fertilization occur, the zygote is formed and the ovary begins to differentiate into the fruit. The outer wall of the ovary begins to differentiate into the pericarp whereas the seed develops within the fruit itself.
Types of Fruits
Fruits can be classified in many ways.
- True and False Fruits
- Simple, Aggregate, and Multiple Fruits
- Simple fruits are further classified as fleshy and dry fruits depending on their appearance
True and False Fruits
- True Fruits- True fruits are those that are formed solely from the ovary with ovules inside it. No other flower parts form a part of this type of fruit.
- False Fruits-False fruits are formed from the ripened ovary along with some other flower parts like the base or receptacle, the perianth etc.
Simple, Aggregate, Multiple and Accessory Fruits
These fruits are formed from a single pistil only. They are further divided into Fleshy and Dry fruits based on the nature of their pericarp and its layers.
I. Fleshy Fruits
Fleshy fruits, as the name mentions, have a fleshy and juicy pericarp. They are further of many different types:
- Drupe- In this type of fleshy simple fruit, the exocarp is thin, the mesocarp is thick and juicy while the endocarp is stony. Examples of such fruits are mango, plum, and coconut.
- Berry- In this type of fleshy fruits, the endocarp is absent and the seeds are scattered in the mesocarp. Examples are grapes, banana, tomato.
- Pome- Is a false fruit as the thalamus forms a part of the fruit. Examples of this type of fruit are apples, pears.
II. Dry fruits
Dry fruits do not have juicy or thick pericarps and are of two types.
- Dehiscent dry fruits
These fruits burst on their own to release the seeds. They are of many types:
- Follicle- These fruits are formed from a single carpel and dehisce along one suture or margin only. Ex: Calotropis
- Legume- These fruits are formed from a single carpel and dehisce along both sutures. Ex: legumes, beans
- Capsule- Is formed from multiple carpels. It has many pores or chambers in it and it dehisces by splitting into many parts to release seeds. Example: Lady’s Finger
- Siliqua-It is formed by two carpels and dehisces from the base upwards with the seeds attached to the base itself. Example: mustard
- Indehiscent dry fruits
These fruits do not dehisce or burst to release the seeds. They are of many types:
- Achene: Is single-seeded and the seed coat is separate from the fruit coat or pericarp. Example: Magnolia
- Caryopsis: Is similar to the achene except that the seed coat and the fruit coat are united or fused. Example: Maize
- Samara: One-seeded fruit with wings. Example: Hiptage, Ash
- Nut: One-seeded fruit with a stony pericarp. It may contain husk on its wall as well. Example: Oak, Chestnut
- Cypsela: Is formed from a bicarpellary inferior pistil. It is also one-seeded. Example: Sunflower
These fruits are developed from an aggregate or cluster of multiple separate pistils that are borne on a single flower. This aggregate or group of fruits that are developed from a single flower are known as an etaerio. Example: Raspberry.
When an entire inflorescence develops into a single fruit, it is called a multiple fruits. Example: Pineapple, figs, mulberry, jackfruit.
Once fertilization occurs, the mature ovule begins to differentiate into a seed. A seed contains many parts, namely:
- Seed Coat– is formed from the integuments of the ovule. The seed coat contains a hilum which is a scar that represents the spot where the ovule was attached to the ovarian wall. The seed coat is present all over the seed except for a small pore called as the micropyle which the where the new plant will germinate on finding a favorable environment.
- The cotyledons-Monocots contain a single cotyledon whereas the dicots contain two cotyledons.The two cotyledons act as appendages and help in absorption of food from the endosperm.
- Endosperm– It is a triploid tissue that is formed by the fusion of one of the male nuclei(haploid) and the vegetative nuclei(diploid). The endosperm functions to provide nutrition to the developing embryo.Learn more about the Endosperm development here.
- Seeds can be classified as endospermic and non-endospermic seeds. Those seeds that utilize the endosperm during the embryo development completely are called as non-endospermic seeds. Those seeds which do not completely utilize the endosperm during the growth of the embryo, are called as endospermic seeds.
- Embryo– is made up of a central axis that contains two ends- the root apex and the radicle, and the shoot apex and the hypocotyl. The radicle gives rise to the primitive root whereas the hypocotyl gives rise to the primitive shoot.
Solved Example for You
Q1: Which of the following fruits have a missing endocarp and the seeds are found scattered in the mesocarp?
Sol. The correct answer is the option ”a”. Examples of this type of fruits are grapes, banana, tomato.