Fruit

For other uses, see Fruit (disambiguation).

In botany, a fruit is the part of a flowering plant (angiosperm) that holds the seeds. It grows from the ovary after the plant flowers.

Fruits help flowering plants spread their seeds. Edible fruits have long moved around with the help of humans and other animals. This is a symbiotic relationship, which means both sides benefit. The plant gets seed dispersal, and the animal gets nutrition. Humans and many other animals depend on fruits for food. Because of this, fruits make up a large part of the world's agricultural output. Some fruits, such as the apple and the pomegranate, also have special meanings in many cultures.

In everyday language and cooking, "fruit" usually means the soft, fleshy parts of a plant that surround the seeds. These are often sweet or sour and can be eaten raw. Examples include apples, bananas, grapes, lemons, oranges, and strawberries. In botany, however, the word covers many more things that people do not usually call fruit. These include nuts, bean pods, corn kernels, tomatoes, and wheat grains.

Botanical vs. culinary

See also: Vegetable § Terminology

Many everyday words for fruit and seeds do not match how plants are scientifically classified. In botany, a fruit is a ripened ovary or carpel that contains seeds. Examples include an orange, pomegranate, tomato, or pumpkin. A nut is a type of fruit, not a seed. A seed is a ripened ovule. In cooking, a fruit is the sweet or sour part of a plant, such as a peach, pear, or lemon. Nuts are hard, oily, plant foods in shells that are not sweet, such as hazelnut or acorn. So-called vegetables are usually savory or not sweet, such as zucchini, lettuce, broccoli, and tomato. Some, like sweet potato, taste sweet.

Many things called vegetables are botanically fruits. These include cucumber, pumpkin, and squash or other winter squashes. All of these are cucurbits. They also include beans, peanuts, and peas, which are all legumes. Corn, eggplant, bell pepper (also called sweet pepper), and tomato are fruits too. Many spices are also fruits, such as black pepper, chili pepper, cumin, and allspice. In contrast, rhubarb is often called a fruit when used in pies, but the part we eat is actually the leaf stalk, or petiole. Botanically, a cereal grain such as corn, rice, or wheat is a kind of fruit called a caryopsis. Its fruit wall is thin and fused to the seed coat, so almost all the part we eat is actually a seed.

Structure

The outer layer of most fruits is called the pericarp. It can be eaten in many fruits. It usually forms from the ovary and surrounds the seeds. In some plants, other parts of the plant add to the edible part or make up the whole thing. The pericarp has three layers, from outside to inside: the epicarp, mesocarp and endocarp. A fruit with a sharp, pointed tip is said to be beaked.

Development

A fruit forms after one or more flowers are fertilized and mature. The gynoecium, the central part of the flower, forms all or part of the fruit. Inside the ovary are one or more ovules. In a process called double fertilization, the ovules turn into seeds. First, pollen moves to the stigma-style-ovary system in a step called pollination. Then a pollen tube carries sperm down to the ovule. One sperm joins the egg to form a zygote, which becomes the seed's embryo. The other sperm helps form endosperm, a food-storing tissue that the embryo uses.

Fruit formation is linked to meiosis, an important part of reproduction in flowering plants. During meiosis, homologous chromosomes copy themselves, recombine, and separate. Then sister chromatids separate to make haploid cells. As the ovules become seeds, the ovary ripens. Its wall, the pericarp, may become juicy and fleshy, as in berries or drupes. It may also form a hard outer shell, as in nuts. Some flower parts, such as sepals, petals, and stamens, may fall away as the fruit ripens. When other flower parts make up a large part of the fruit, it is called an accessory fruit. Examples include apples, rose hips, strawberries, and pineapples.

There are three general ways fruit develops:

• Apocarpous fruits develop from a single flower with separate carpels. These are the simple fruits.
• Syncarpous fruits develop from a single gynoecium with two or more carpels fused together.
• Multiple fruits form from many flowers growing in one cluster.

Types

Plant scientists sort fruits into three main groups: simple fruits, aggregate fruits, and multiple fruits. These groups depend on how the ovary and other flower parts are arranged and how the fruit grows. The groups do not show how closely plants are related, because very different taxa can be in the same group. Simple fruits come from one ovary in a flower with a single pistil. Dry simple fruits include the achene, capsule, and caryopsis. Cereal grains such as wheat, rice, oats, and barley are examples. Some dry fruits split open to release their seeds. This is called dehiscence. Others stay closed and wait to break down or to be carried off by frugivores, which are animals that eat fruit. Fleshy simple fruits include berries, stone fruits or drupes, such as apricot, cherry, olive, peach, plum, and mango. They also include pomes, such as apples and pears.

Aggregate fruits grow from one flower that has many simple pistils. The small fruitlets join together. The raspberry is one example, and magnolia and peony are others. Multiple fruits form from a cluster of flowers, called an inflorescence. The fruitlets merge into one mass, as in a fig or mulberry. Some fruits, such as tayberry and strawberry, were created by people by mixing plants to make new varieties. These are grown as new cultivars. The "fruiting body" of a fungus that makes spores has a similar name, but fungi belong to the fungi kingdom, not the plant kingdom.

Seedless fruits

Some fruits are sold without seeds, and many people like them this way. Commercial cultivars of bananas and pineapples are seedless fruits. Some kinds of citrus fruits, table grapes, and watermelons are also valued because they have no seeds.

In some plants, fruit forms without fertilization. This is called parthenocarpy. It may or may not need pollination, but most seedless citrus fruits need a signal from pollination to grow. Seedless bananas and grapes are triploids. Their seeds do not develop because the embryonic plant made by fertilization stops growing. This is called stenospermocarpy, and it needs normal pollination and fertilization first.

Seed dispersal

Fruits come in many shapes because each kind spreads its seeds in a different way. Seeds may travel by wind or water, by explosive dehiscence, or with the help of animals. Some fruits have spiky or hooked outer coats. These either keep animals from eating them or catch on fur, feathers, legs, or clothing, so the seeds are carried away. Plants that spread seeds this way are called zoochorous. Common examples include cocklebur, unicorn plant, and beggarticks (or Spanish needle). Juicy fruits attract hungry animals. The animals eat them, carry the seeds away, and later drop them (defecated) far from the parent plant. Oily nuts attract birds and squirrels, which hoard them by burying them in the soil for winter. Seeds that are never dug up can germinate and grow into new plants some distance away.

Other fruits have flat, winglike blades or fluffy "parachutes" that let the wind carry seeds farther. Examples include elm, maple, tuliptree, dandelion, milkweed, and salsify. Coconut fruits can float in the ocean for a long time. Nipa palm and screw pine can also spread by water. Some fruits fling their seeds with force. The sandbox tree can throw seeds up to 100 m (330 ft). Impatiens and squirting cucumber also spread their seeds this explosive way.

Food uses

Many fruits are good to eat. People eat them fresh or cook them into fruit preserves, such as jams and marmalade. Fruits are also used in foods and drinks, including alcoholic beverages, fruit beer, and wine. Some spices, such as vanilla, black pepper, paprika, and allspice, come from berries. Olives are pressed to make olive oil. Some fruits can be found all year, while others are only seasonal. Fruits are also given as fruit baskets and fruit bouquets. To keep fruit fresh after it is picked, it helps to store it in a cold chain. Many fruits release a plant hormone called ethylene, which causes them to ripen.

Eating fruit and vegetables is linked to lower signs of inflammation, which is the body's way of reacting to harm or illness. It is also linked to a stronger group of gamma delta T cells, which help the body fight sickness. Many fruits contain fiber and water, and many are high in vitamin C. Fiber helps people feel full (satiety). It may also help control body weight and lower blood cholesterol. High cholesterol is a risk factor for cardiovascular diseases, which affect the heart and blood vessels.

To keep fruit safe to eat, the CDC suggests washing fruit before eating it. It also suggests keeping fruit away from raw meat, poultry, and seafood. Cut fruit should be put in the fridge within two hours. These steps help lower the risk of food contamination and foodborne illness. Some people are allergic to fruit. Fruit allergies make up about 10 percent of all food allergies.

Nonfood uses

People have eaten fruit for a very long time, so many cultures have found other uses for fruits. Bayberry fruits give a wax that is often used to make candles. Many dry fruits, such as annual honesty, cotoneaster, lotus, milkweed, unicorn plant, and wheat, are used as decorations or in dried flower arrangements. Some ornamental trees and shrubs, including beautyberry, cotoneaster, holly, pyracantha, skimmia, and viburnum, are grown for their colorful fruits.

The fruits of the opium poppy are the source of opium. Opium contains codeine and morphine. It also contains the chemical thebaine, which is used to make oxycodone. Osage orange fruits are used to keep away cockroaches. Many fruits, such as cherry, mulberry, sumac, and walnut, can be used to make natural dyes. Dried gourds are used to make bird houses, cups, decorations, dishes, musical instruments, and water jugs. Pumpkins are carved into Jack-o'-lanterns for Halloween. The fibrous inside of a mature, dry Luffa fruit is used as a sponge. The spiny fruit of burdock or cocklebur inspired the invention of Velcro. Coir fiber from coconut shells is used to make brushes, doormats, and many other things. The shells are also used to make bowls, cups, and bird houses. The hard, colorful grain fruits of Job's tears are used as decorative beads.