The Fruit and Layers of the Pericarp

A fruit develops from a flower

One of the defining features of flowering plants is that seeds normally become enclosed within an ovary-derived fruit. After successful fertilisation, the ovules develop into seeds while the ovary grows and matures into a fruit. This connects flower morphology directly with reproduction and dispersal: tissues that surrounded young ovules in a flower can later protect developing seeds and assist their movement to new locations.

Fruit development involves many tissue changes. Ovary tissues may become juicy, leathery, papery, fibrous or hard, depending on the plant. The number of ovules that developed and the type of ovary contribute to the structure of the mature fruit. Because different fruit types develop in different ways, not every edible sweet plant part is botanically a true ovary-derived fruit; when describing a specific specimen, identify the developmental organ rather than relying on its use in cooking.

The pericarp is the fruit wall

A usual fruit contains one or more seeds enclosed by a surrounding fruit wall known as the pericarp. In some fruits the pericarp dries as the fruit matures; in others it becomes thick and fleshy. In a thick pericarp, three layers can be distinguished. The epicarp is the outermost layer, the mesocarp is the middle, and the endocarp is innermost, next to the seed-bearing cavity. These layers are parts of the fruit wall, not layers of the seed coat.

Mango and coconut: two distinct drupes

A drupe is a fruit type with a differentiated pericarp and commonly a hard endocarp surrounding a seed. Mango provides an especially clear example. Its thin outer epicarp forms the skin, the thick succulent mesocarp forms most of the edible pulp, and the inner endocarp is woody and stony around the seed. Thus the edible mango flesh is part of the fruit wall rather than a cotyledon of the seed.

Coconut is also a drupe, but its middle mesocarp is prominently fibrous rather than soft and juicy. The hard inner shell corresponds to its endocarp, enclosing the seed. A coconut sold for food is often missing much of the external husk, so comparing a market coconut with a whole fruit can be misleading unless the removed outer layers are considered. Both mango and coconut typically develop from a single carpel-bearing superior ovary and are one-seeded in the familiar textbook descriptions.

Fruits can also develop without fertilisation

Parthenocarpy means fruit formation without fertilisation of the ovules. Such fruits are often seedless or have incompletely developed seeds because the usual fertilisation-dependent embryo development did not occur. Parthenocarpy can occur naturally in some crops and may also be induced during cultivation. It is different from vegetative propagation, where new plants develop from non-reproductive structures; parthenocarpy still produces a fruit from flower tissue.

Recognising a fruit in section

To study a fleshy fruit, draw a clean cross-section and mark the outermost wall, middle tissue and inner layer adjacent to the seed. Try tracing each region from outside inward rather than naming layers by colour. Some fruits do not show all three layers distinctly, and the categories dry and fleshy do not automatically tell you the number of seeds. In a drupe, the often-stony endocarp makes the layers unusually easy to distinguish.

The biological role of fruits extends beyond protecting seeds. Fleshy tissue may attract animals that disperse seeds, whereas dry structures can help release them by splitting or by movement in wind and water. The chapter focuses on the structural relationship of fruit and seed, which is the foundation for interpreting such dispersal adaptations.

Quick Quiz

Model Answers

1. A fruit is the mature ovary in the typical pattern. Its pericarp is the wall derived from the ovary wall, while seeds develop from the ovules it encloses.

2. Epicarp outermost; mesocarp in the middle; endocarp innermost near the seed. These layers may have different textures.

3. Both display a differentiated pericarp with a hard inner endocarp surrounding the seed. Mango has fleshy mesocarp; coconut has fibrous mesocarp.

4. Parthenocarpy produces fruit without ovule fertilisation, whereas normal sexual seed formation follows fertilisation and embryo development inside the ovule.