SS3 First Term Biology Lesson Note – Fruit

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WEEK 5

SUBJECT: BIOLOGY                                                 

TOPIC: FRUIT

CONTENT: 1. Structure of fruits

2. Types of fruits
3. Dispersal of fruits
4. Agents of dispersal

SUB-TOPIC I: MEANING OF FRUIT

Fruit is the structure that developed from the matured ovary after fertilization which contains the seed. Some fruits do not develop from fertilized ovary and are called parthenocarpic fruit.

Fruit contains the pericarp (epicarp, mesocarp and endocarp).

TYPES OF FRUITS

Fruits can be classified based on their origin or structure. These include:

• True and false fruit
• Simple, aggregate and composite (multiple) fruit
• Fleshy and dry fruit
• Dehiscent and indehiscent fruits

Simple fruits: Formed from one flower having either a monocarpous or syncarpous pistil.

Aggregate fruits: Formed from one flower having an apocarpous pistil

Multiple fruits: these are fruits formed from many flowers whose ovaries unite together with other parts of the flower after fertilization or one that develops from several flowers inflorescence e.g. pineapple, bread fruit etc.

SIMPLE FRUITS

The simple fruits can be divided into dry and fleshy fruits. A dry fruit is the type of fruit in which the pericarp becomes dry, hard and woody or fibrous when the fruit ripens. Dry fruit may be dehiscent or indehiscent.

DRY DEHISCENT FRUIT: These are fruit with hard and dry pericarp which can split to release their seeds. The dry dehiscent fruit can be divided into five namely: the follicle, legumes, schizocarps, capsule and Siliqua

Follicle: The follicle are fruits that are formed from one carpel and which can split along one side only e.g. kola

Legume: These are fruits that are formed from one carpel that splits along two sides e.g. cowpea, crotolaria and all bean species

Capsule: These are fruits formed from fused carpels and split longitudinally along two or more lines e.g. okra, castor oil and cotton

Schizocarps: These are many seeded fruits which break up into one seeded parts called mericarp e.g. Mimosa pudica (sensitive plant) and Desmodium

Siliqua: A long narrow capsule formed from bicapellary ovary. It has two chambers separated by a false septum or reptum. It dehisces by the sutures e.g. Teconia

DRY INDEHISCENT FRUITS: These are the fruits that do not split to release their seeds. Dry indehiscent fruits are divided into five.

Achene: The fruit has dry pericarp and contain one seed e.g. cashew, nut, sunflower fruit, four O’clock plant, rose and clematis

Caryopsis: the caryopsis is a one-seeded dry indehiscent fruit in which the pericarp becomes fused with testa. Examples are rice, maize and millet

Cypsela: the cypsela is one-seeded dry fruit with hairy pappus and hairy pericarp. Examples are Tridax, Emilia and goat weed.

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