Fruits

A fruit is the mature structure formed from a fertilized ovary. When fruits develop without fertilization, they are called parthenocarpic or seedless fruits.

Parts of a Fruit

Fruits consist of two main parts: the pericarp and the seed. The pericarp forms from the ovary wall and has three layers:

1. Exocarp (Epicarp): The outermost layer, which forms the fruit's skin.
2. Mesocarp: The middle layer, typically fleshy, juicy, or thick.
3. Endocarp: The innermost layer, which may develop into a pith or hard protective covering.

Classification of Fruits

Fruits are broadly categorized into three groups based on the number of ovaries and flowers involved in their formation:

1. Simple Fruits: Develop from a single ovary. Examples:
   • Monocarpous (one ovary): maize, cowpea.
   • Syncarpous (fused ovaries): pawpaw.
2. Aggregate Fruits: Form from multiple ovaries of a single flower. Examples: strawberry, custard apple, and kola nut.
3. Multiple (Composite) Fruits: Develop from the ovaries of multiple flowers (inflorescence). Example: pineapple.

Dry vs. Fleshy Simple Fruits

Simple fruits can be classified as dry or fleshy:

Dry Fruits

In dry fruits, the pericarp becomes hard, woody, or fibrous upon ripening. These are further divided into:

1. Dehiscent Fruits: Split open at maturity. Types include:
   • Follicle: Formed from one carpel, splits on one side. Example: kola.
   • Legume: Formed from one carpel, splits on two sides. Examples: cowpea, beans.
   • Capsule: Formed from fused carpels, splits longitudinally. Example: okra.
   • Siliqua: A long, narrow capsule with a false septum, splits at the sutures. Example: Teconia.
   • Schizocarp: Breaks into single-seeded parts called mericarps. Examples: sensitive plant, Desmodium.
2. Indehiscent Fruits: Do not split open at maturity. Types include:
   • Achene: Dry pericarp enclosing one seed. Examples: cashew, sunflower.
   • Caryopsis: Pericarp fused with the seed coat. Examples: maize, rice.
   • Cypsela: One-seeded fruit with a hairy pappus. Examples: Tridax, goat weed.
   • Nut: Woody or hard pericarp. Examples: almond, groundnut.
   • Samara: Pericarp forms wing-like outgrowths. Examples: African rosewood, obeche tree.

Fleshy Fruits

Fleshy fruits have soft, thickened pericarp layers. Types include:

• Drupe: Thin exocarp, fleshy mesocarp, hard endocarp. Examples: mango, coconut.
Credit: Lulum Leliana on Researchgate
• Berry: Fleshy pericarp with no stony layer. Examples: guava, tomatoes.
• Hesperidium: Segmented chambers with a tough rind. Examples: orange, lemon.
• Pome: Fleshy part forms from the receptacle; the core develops from the ovary. Examples: apples, pears.
Credit: MariStep on Freepik
• Pepo: Hard exocarp and partially enclosed ovary. Examples: pumpkin, cucumber.

Aggregate and Multiple Fruits

Aggregate Fruits: Develop from multiple ovaries of a single flower. Examples: blackberries, raspberries.

Multiple Fruits: Form from the combined ovaries of an inflorescence. Examples: pineapple, mulberry.

Seed Dispersal

Seed dispersal refers to the scattering of seeds and fruits from parent plants. This process helps:

1. Prevent overcrowding.
2. Reduce competition for resources.
3. Promote plant diversity.
4. Introduce plants to new environments.

Agents of Dispersal

The three main methods of dispersal are:

1. Water: Seeds like those of water lilies and coconut use buoyancy to travel.
2. Wind: Seeds are light and often equipped with wings or parachute-like structures. Examples: cotton, sycamore.
3. Animals: Seeds with hooks or spines attach to animals, while others are eaten and dispersed through digestion. Examples: guava, cashew.

Self-Dispersal

Some fruits use explosive mechanisms to eject seeds. Examples include legumes (e.g., Acacia) and oil bean fruits.