FRUIT: INTRODUCTION, TYPES, CLASSES, AND DISPERSAL

Fruits are very essential parts of our diet which aids in the growth of the human body. These fruits when eaten helps fight diseases, acts as a source of vitamin in our diet, aids in healthy growth of the body and lots more. Different fruits play different roles in the human body and as such, they can-not be taken away exclusively from our diet.

A fruit is a fertilized and ripened ovary and the seeds inside the fruit are developed from the Ovules. The ovarian wall becomes the fruit wall or Pericarp. Fruits which develop without fertilization are called Parthenocarpic and are seedless. A true fruit develops solely from the ovary while a false fruit develops from the Receptacle or Calyx.

DIFFERENCES BETWEEN A FRUIT AND A SEED
1. A fruit has two scars while a seed has only one scar.
2. A fruit develops from the ovary while a seed develops from the ovule.
3. A fruit contains seeds while a seed contains embryo.
4. The pericarp of a fruit is formed from the ovarian wall while the testa of a seed is formed from the integument.

TYPES OF FRUITS

CLASSES OF FRUITS
1. SIMPLE FRUITS: These are formed from a single flower with a monocarpous or synocarpous pistil. E.g. okro, bean, and pride of Barbados.
2. AGGREGATE FRUIT; These are formed from a single flower with an apocarpous pistil. E.g. Clematis and Blackbery.
3. MULTIPLE FRUIT: These are formed from whole inflorescence, E.g. Pineapple and the Fig.

The following are the classes of fruits based on the basis of the pericarp texture
a. Dry fruits
b. Fleshy fruits.

DRY FRUITS
These are based on the divisions which are

1. DEHISCENT FRUITS
The dry dehiscent fruits split to release seeds. These include;
a. Follicle which is formed from one carpel and also splits along one side. E.g. Sodom Apple, Cenestis, and Frangipani.
b. Legume which is formed from one carpel and splits along both sides. E.g. Beans, Crotalaria, Pride of Barbados, and Flamboyant.
c. Capsule which is formed from two or more several fused carpel with many seeds and it splits along many lines. E.g. Okro, Cotton and Castor Oil.
d. Schizocarp: These have only one carpel and ovary with many seeds. The fruit breaks into units each enclosing one seed. E.g. Desmodium.

2. DRY INDEHISCENT FRUITS
These fruits do not split to release seeds. Examples are as follows;
a. Achene consists of a single seed surrounded by a dry pericarp. E.g. Sunflower, Butterfly, and Fig plant.
b. Cypsela is an achene formed from two carpels and with a pappus hair above. E.g. Tridax.
c. Nut: this is similar to achene but it has a tough, hard, or stony pericarp. E.g. Cashew Nut.
d. Caryopsis is similar to an achene but the pericarp and seed coat have become fused together. E.g. Maize.
e. Samara with is an achene with pericarp extended to form wings. E.g. Rose Wood and Combretum.

Note that maize is an endospermous seed and has its food reserve (starch and protein) in the endosperm and the cotyledon is called Scutellum.

FLESHY AND SOFT FRUIT

Drupe has thin pericarp made up of three layers namely; the outer thin layer called Epicarp, the middle fleshy layer called the Mesocarp fibrous in coconut and the inner hard layer enclosing the seed called the Endocarp. The drupe is derived from a single carpel and it’s usually one seeded. E.g. Mango, Plum, coconut, and Palm Nut.

Berry is a true fleshy simple fruit derived from a syncarpous ovary and are with many seeds embedded in the flesh. The three layers of pericarp are all fleshy. The mesocarp and endocarp are fused. E.g. are Tomatoes and Oranges.

Hesperidium is similar to berry but the endocarp is projected inwards forming distinct chambers, and the epicarp and the mesocarp are fused together to rind (loose or tight skin) of fruits. Chambers contain succulent hairs attached to the endocarp. E.g. Lemon, Orange, Lime and Grape fruits.

DISPERSAL OF FRUITS AND SEEDS
Seeds and fruits are dispersed to avoid overcrowding and also helps to cover barren areas with vegetation.

METHODS OF FRUITS AND SEED DISPERSAL
WIND
A. Small and light seeds. E.g. seeds of grasses and Orchids.
B. Floss around the seeds. E.g. Cotton.
C. Fruits with parachute or pappus. E.g. Tridax.
D. Winged seeds. E.g. Tecoma and fruits. E.g. Combretum.

WATER
Seeds and fruits with air spaces to enable them from floating in water. E.g. seeds of water lilies, and coconut with fibrous mesocarp.

ANIMALS
A. Fruits and seeds with hooks. E.g. Triumphetta and Mimosa which when caught in the fur of animals can be dropped away from the parent plant.
B. Fruits with sticky hairs can adhere on the skin or fur of animals and get dispersed by them. E.g Desmodium.
C. Fleshy fruits eaten by animals and man and the seeds thrown away. E.g. Orange and Mango.
D. Sticky substances on the seeds that adhere to the beaks of birds which eat the fruits can be brushed off. E.g. Mistletoe is dispersed by birds.

EXPLOSIVE MECHANISMS
Scattering of the seeds by splitting of the fruit wall due to the drying of the pericarp. E.g. Castor oil, Oil bean fruits, and Balsam fruit.

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