Structure of a fruit - SS3 Biology Lesson Note

The structure of a fruit can vary depending on the type of fruit and the plant species. However, most fruits have common components and structures. Here is an overview of the typical structure of a fruit:

1.       Pericarp: The pericarp is the wall of the fruit, and it consists of three layers:

·         Exocarp: The outermost layer of the pericarp is called the exocarp or the skin. It can vary in thickness, texture, and colour, depending on the fruit type. In some fruits, such as apples or peaches, the exocarp is relatively thick and smooth, while in others, such as oranges or grapes, it may be thin and easily peelable.

·         Mesocarp: The middle layer of the pericarp is the mesocarp. It is typically the fleshy part of the fruit, surrounding the seeds. The mesocarp can vary in texture and composition, ranging from juicy and pulpy in fruits like berries or tomatoes to firm and fibrous in fruits like apples or pears.

·         Endocarp: The innermost layer of the pericarp is the endocarp. It directly surrounds the seeds and can have various structures. In some fruits, such as cherries or peaches, the endocarp forms a hard, stony layer known as the pit or stone. In other fruits, such as citrus or grapes, the endocarp is thin and not easily distinguishable.

2.       Seed(s): The seed(s) is the reproductive structure within the fruit. Seeds contain the genetic information and resources necessary for the development of a new plant. Fruits can have a single seed (e.g., cherry, peach) or multiple seeds (e.g., apple, watermelon), depending on the species.

3.       Carpels or Ovaries: Fruits originate from the mature ovaries of flowers. The carpels, which are the female reproductive organs of the flower, develop into the fruit after pollination and fertilization. The number of carpels in a flower can vary, resulting in different fruit structures, such as simple fruits (from a single carpel), aggregate fruits (from multiple carpels in a single flower), or multiple fruits (from multiple flowers).

4.       Receptacle: The receptacle is the base of the flower from which the fruit develops. In some fruits, the receptacle becomes part of the fruit structure, such as the enlarged and fleshy receptacle in strawberries or figs.

The structure of a fruit is intricately linked to its role in seed dispersal and protection. Fruits are adapted to attract animals or utilize various mechanisms to aid in the dispersal of seeds. The diversity in fruit structure contributes to the wide array of fruit types we encounter, from berries and drupes to pods and capsules, each with their unique characteristics and adaptations.