Fruits: Definition, structure, and classification

A fruit is a mature fertilized ovary of a flower containing one or more seeds.

 However, in certain plants, e.g banana and pineapple, fertilization is not necessary for fruit formation.

Fruits which develop without fertilization are known as partenocarpic fruits and they are often seedless. Generally, the result of pollination and fertilization in flowers is the formation of fruits and seeds.

Now let look at the structure of a fruit

Structure of a fruit

The structure of a typical fruit, e.g mango is made up of an outer covering called the epicarp , middle layer called mesocarp and an inner layer called the endocarp. Within the endocarp is the seed(s).

The epicarp, mesocarp and endocarp of a fruit is collectively called the pericarp.

A fruit normally consist of the following parts :

• The fruit wall or pericarp
• The seed or seeds inside the fruit
• The remains of the style or scar showing point of attachment of the style.
• The fruit stalk or scar showing point of attachment of the fruit to the plant.

Classification of Fruits

Fruits are classified into different groups depending on their origin and structure. The following are the common ways of classifying fruits:

• Fleshy and dry fruits
• True and false fruits
• Dehiscence and indehiscent fruits
• Simple, aggregate and composite fruits

Fleshy and Dry Fruits

Fruits may be classified into fleshy and Dry usually according to the nature of their pericarps.

Fleshy Fruits

A fleshy Fruit is the type of fruit in which the whole pericarp or at least one of it layers is thick , soft, and fleshy especially when it is ripe.

Types of fleshy Fruits

Drupe: The pericarp of a drupe consist of three layers, namely mesocarp, epicarp, and endocarp. 

The epicarp is thin, the mesocarp may be fibrous, e.g coconut and oil palm nut or fleshy, e.g mango, while the endocarp I hard and Stony. In mango, the fleshy mesocarp is the edible part and the endocarp encloses the seed . 

 The common examples of drupe are mango, coconut and palm nut.

Berry : The pericarp of a berry also consist of three Layers which are ; thin epicarp, succulent mesocarp, and endocarp. The endocarp in berry is not had and Stony as in drupe.  It is soft and fleshy. 

Examples of berries are; tomatoes,guava ,melo melon , Orange, pawpaw and pepper. In tomatoes the seeds are scattered within the mesocarp and endocarp, while in orange, it has distinct chambers separated by sheets of endocarp. It has one seed in one chamber.

Pome: pome is a simple false fruit in which the skin and the fleshy edible part are derived from the receptacle and only the core enclosing the seeds are from the ovary. Examples of pome are apples and pear.

Sorosis: is a composite false fruit formed from a dense of florescence. Every part of each flower forms part of the fruit while the stalk or axis of the inflorescence swells to form the core or mass. 

 The pineapple and breadfruits are examples of sorosis.

True and false fruits

True Fruits 

A true fruit is the type of fruit that develops solely from a fertilized ovary. It consist of a pericarp and seed or seeds. Examples of these type of fruits are; mango, orange, and cowpea.

False Fruits

A false fruits are the type of fruits formed from ovary and other Floral part as well. Examples of these type of fruits are; cashew, pineapple, apple.

Simple Aggregate and Composite Fruits

Simple Fruits: They are fruits developed from a flower with a single ovary. The ovary may be monocarpous as in cowpea and maize or syncarpous as in okra, tomato and pawpaw.

Aggregate Fruits: They are fruits which develops from a single flower with several ovaries. 

Such flower has pistil where the carpels are separated and so have several ovaries. Each ovary develops into a fruitlet . Examples of these type of fruits are Kola, apple and strawberry.

Composite Fruits: A composite Fruit is a fruit that develops from an inflorescence (several flowers) or flowers positioned very close to one another. 

Here, all the fruitlets and the floral parts are fused together to form a single large false fruit. Examples of this type of fruit is the pineapple.

Dry Fruits

A dry fruit is a fruit in which the pericarp becomes dry, hard and Woody or fibrous when the fruit ripens. 

Dehiscent and indehiscent Fruits

Practically, all freshly Fruits are indehiscent while dry fruits may be dehiscent or indehiscent. 

Fruits may also be grouped into dehiscent or indehiscent depending on whether their pericarps split when ripe or not.

Dry Dehiscent Fruits 

These Fruits are the Fruits which split to release their seed when ripe, leaving the fruit wall on the plant. The types of this fruit are legumes, follicle capsule and schizocarp.

Legumes or pods : a legume or pod is a simple fruit formed from a superior monocarpous pistil. 

It's usually long and fattened side ways.when the fruit is ripe, the pericarp dehisces longitudinally along both sides to release the seeds inside it. 

Examples of legumes are found in the legumes family such as cowpea, soybeans, pride of Barbados.

Capsule: The fruit of capsule ia formed from a single ovary divided into many independent compactments called carpels. Examples of capsule are okra fruit, cotton etc.

Follicle: a follicle is a simple fruit formed from a superior monocarpous pistil. The ripe fruit dehisces longitudinally on side only. 

Examples of follicle are silk cotton and kola.

Schizocarp: They're formed from an ovary made up of one carpel. The dry fruit has several seeds and breaks up into units, each enclosing one seed. Examples of schizocarp are cassia and desmodium 

Dry indehiscent Fruits

These are Fruits which do not split open when mature or ripe , but usually fall to the ground where the pericarp eventually decays to release the seeds. Such fruits are often very small and are produced in large numbers. Types of these Fruits are nut , Samara, Cypsela etc.