Fruit

Development

A fruit results from the fertilizing and maturing of one or more flowers. The gynoecium, containing the stigma-style-ovary system, is centered in the flower-head and forms all or part of the fruit. Inside the ovary are one or more ovules, where a complex sequence called double fertilization begins: a female gametophyte (megagametophyte or embryo sac) produces an egg cell. After double fertilization, the ovules become seeds.

Pollination, the movement of pollen from stamens to the stigma-style-ovary system, initiates the process. A pollen tube then grows from the deposited pollen through the stigma and style into the ovary to the ovule, transferring two sperm to the megagametophyte. One sperm unites with the egg to form a zygote, while the second enters the central cell to form the endosperm mother cell, completing double fertilization.

The zygote later gives rise to the seed embryo, and the endosperm mother cell produces endosperm, a nutritive tissue. Fruit formation involves meiosis, a central aspect of sexual reproduction in flowering plants. As ovules develop into seeds, the ovary ripens and its wall, the pericarp, may become fleshy or form a hard outer covering. The pericarp typically differentiates into two or three distinct layers: exocarp (epicarp), mesocarp, and endocarp.

Classification

Fruits are grouped into three main categories by plant scientists: simple, aggregate, and multiple (or composite). These categories are based on how the ovary and other flower parts are arranged and how the fruit develops, not on evolutionary relationships, since different plant families can fall into the same group. A simple fruit comes from a single flower with one pistil, where a simple or compound ovary ripens.

A single flower with many pistils usually forms an aggregate fruit, while a cluster of multiple flowers merging together creates a multiple fruit. Simple fruits are either dry or fleshy. Dry fruits can split open to release seeds (dehiscence) or rely on decay or animals eating and excreting the seeds (indehiscence).

Fleshy fruits never split open and often depend on animals for seed dispersal. Examples of dry simple fruits include achene, capsule, caryopsis, cypsela, fibrous drupe, follicle, legume, loment, nut, samara, schizocarp, silique, silicule, and utricle. Fleshy simple fruits have a pericarp that is partly or fully fleshy when ripe.

Seed dispersal

Variations in fruit structures largely depend on the modes of seed dispersal. Dispersal is achieved by wind or water, by explosive dehiscence, and by interactions with animals. Some fruits have outer skins or shells coated with spikes or hooked burrs, which either deter foragers or attach to animal hair, feathers, legs, or clothing, using animals as dispersal agents; such plants are termed zoochorous. Through mutual evolution, fleshy fruits appeal to hungry animals, which ingest seeds and later deposit them at a distance.

Nutritious, oily kernels of nuts motivate birds and squirrels to hoard and bury them, effectively sowing uneaten seeds. Other fruits have flattened, elongated wings or helicopter-like blades for wind dispersal, while some have tiny parachutes. Coconut fruits can float in the ocean to spread seeds, as can nipa palm and screw pine. Some fruits have propulsive mechanisms that fling seeds substantial distances, up to 100 m in the case of the sandbox tree.

Food uses

Fruit baskets and bouquets are common gifts and social offerings. Many items we call vegetables in the kitchen are actually botanical fruits, including tomatoes, green beans, bell peppers, cucumbers, eggplants, okra, pumpkins, squash, and zucchini; these are sold daily at markets and greengrocers for cooking. After harvest, proper care matters.

The plant hormone ethylene triggers ripening in many fruits, so keeping them in an efficient cold chain helps extend their shelf life. An analysis of 83 studies linked fruit and vegetable intake to lower inflammation markers and a stronger immune cell profile. Culinary fruits often provide fiber, water, and plenty of vitamin C. The fiber in fruit promotes a feeling of fullness, which can help with weight control and lowering blood cholesterol, a factor in heart disease. Research is exploring how fruit consumption may improve nutrition and influence chronic conditions.

For safety, the CDC advises careful handling: pick undamaged produce, refrigerate precut pieces, and rinse all fruits and vegetables before eating, even those with inedible skins. Keep them separate from raw meat, poultry, seafood, eggs, and any utensils that have touched these items. Discard any uncooked produce that has contacted raw animal products.

Did You Know?

• Bayberry fruits provide a wax often used to make candles.
• Many dry fruits are used as decorations or in dried flower arrangements, including annual honesty, cotoneaster, lotus, milkweed, unicorn plant, and wheat.