Session 13 Reading
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FRUIT INTRODUCTION
Fruit, mature ovary in flowering plants, together with all inseparably connected parts of the
flower. In strict botanical usage, the meaning may be restricted to the ovary alone. Commonly
the term fruit is often restricted to succulent, edible fruits of woody plants, to melons, and to
such small fruits as strawberries and blueberries. In nature, fruit is normally produced only
after fertilization of ovules has taken place, but in many plants, largely cultivated varieties
such as seedless citrus fruits, bananas, and cucumbers, fruit can matures without fertilization
In either case, the maturation of the ovary results in the withering of stigmas and anthers and
enlargement of the ovary or ovaries. Ovules within fertilized ovaries develop to produce
seeds. In unfertilized varieties, seeds fail to develop, and the ovules remain their original size.
The major service performed by fruit is the protection of developing seeds. In many plants,
fruit also aids in seed distribution. See Seed.
Strictly defined, the fruit of a flowering plant is its mature, swollen ovary. Pollen grains (the male gametes, carried
from the anther of one flower to the stigma of another flower by a foraging insect) germinate on the stigma,
growing down the style and into an ovule, where they may fertilize the egg within. If fertilized, the ovules develop
into seeds, and the receptacle protecting the ovary enlarges to form what we recognize as the flesh of the fruit.
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STRUCTURE OF FRUIT
As the ovary matures, its wall develops to form the pericarp, divided into three layers. The
outermost, exocarp, is usually a single epidermal layer. The extent of the middle layer, mesocarp,
and the inner layer, endocarp, varies widely, but in any single type of fruit one of the layers may
be thick, the others thin. In fleshy fruits the pulpy layer is usually the mesocarp, as in peaches or
grapes. The seed or seeds, which lie immediately within the pericarp, in some cases constitute
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the entire edible portion of the fruit. For example, the hard outer husk of a coconut is the
complete pericarp, and the edible part inside, including the "milk," is the seed.
In typical cases, the fruit is confined to the ripened ovary, as in the pea pod; but in apples it
includes ovary plus receptacle (other fused floral parts), in strawberries it is an aggregation of
small individual fruits on a fleshy receptacle, called achenes, and in pineapples it is a
development of an entire inflorescence, or cluster of flowers.
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TYPES OF FRUIT
Fruit is classified by several characteristics, the most significant being the number of ovaries
included. A simple fruit is a single ovary, developed from the pistil of a single flower, which
may be single or compound; an aggregate fruit is composed of many ovaries attached to a
single receptacle; a multiple, or collective, fruit is formed from the coalesced ovaries of an
entire inflorescence. Simple fruits are further subdivided into two categories, dry or fleshy.
Ovary walls that develop into simple fruits are succulent when young, but as they mature,
those of dry fruits lose most of their moisture, whereas those of fleshy fruits increase in size
and moisture capacity. Dry fruits that dehisce, or split, when ripe are called dry dehiscent
fruits; those that do not are indehiscent fruits.
The lemon tree bears large numbers
of fruit throughout the year. The
fruit, or hesperidium, is sold fresh,
while the pulp of the fruit is used to
produce frozen concentrate and fresh
juice. The skin, or rind, contains oil
used in the manufacture of perfume
and lemon flavoring.
Oxford Scientific Films
The true nut, as exemplified by the European, or
sweet, chestnut, is a dry fruit with one seed enclosed
in a hard, thick pericarp. True nuts do not split open
when ripe. Other examples of true nuts are the
hazelnut, beechnut, and acorn.
Oxford Scientific Films
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The rock melon, or cantaloupe, has a soft
rind with a distinct netted appearance and
a soft, juicy, salmon-colored pulp. Melon
plants, belonging to the gourd family,
produce many varieties of sweet fruit.
Oxford Scientific Films
Indigenous peoples in South America cultivate
the native pineapple tree for its succulent fruit.
Having been introduced to other parts of the
world, the trees are now cultivated almost
exclusively in tropical and subtropical regions.
Oxford Scientific Films
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FOOD VALUE
Fruits are eaten raw or cooked, dried, canned, or preserved. Carbohydrates, including
starches and sugars, constitute the principal nutritional material. Citrus fruits, tomatoes, and
strawberries are primary sources of vitamin C, and most fruits contain considerable quantities
of vitamin A and vitamin B. Vitamin content is sharply reduced in storage and shipping of
fresh fruits, but is maintained efficiently in frozen fruit. The jelly-making quality of many fruits
is due to pectin, an important carbohydrate constituent. In general, fruits contain little protein
or fat. Exceptions are avocados, nuts, and olives, which contain large quantities of fat, and
grains and legumes, which contain considerable protein. Although the edible portions of fruits
have a small ash content, fruits supply an important part of the mineral matter necessary in
human diet. Dried or evaporated fruits contain much more nutritional material in proportion to
their bulk than do fresh fruits, due to concentration by evaporation.
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