The development sequence of a typical
drupe, the
nectarine (
Prunus persica) over a 7.5 month period, from bud formation in early winter to fruit ripening in midsummer (see
image page for further information)
Main article:
Fruit anatomy
A fruit results from maturation of one or more flowers, and the
gynoecium of the flower(s) forms all or part of the fruit.
[9]
Inside the ovary/ovaries are one or more
ovules where the
megagametophyte contains the egg cell.
[10] After
double fertilization, these ovules will become seeds. The ovules are fertilized in a process that starts with
pollination,
which involves the movement of pollen from the stamens to the stigma of
flowers. After pollination, a tube grows from the pollen through the
stigma into the ovary to the ovule and two sperm are transferred from
the pollen to the megagametophyte. Within the megagametophyte one of the
two sperm unites with the egg, forming a
zygote,
and the second sperm enters the central cell forming the endosperm
mother cell, which completes the double fertilization process.
[11][12] Later the zygote will give rise to the embryo of the seed, and the endosperm mother cell will give rise to
endosperm, a nutritive tissue used by the embryo.
As the ovules develop into seeds, the ovary begins to ripen and the ovary wall, the
pericarp, may become fleshy (as in berries or
drupes),
or form a hard outer covering (as in nuts). In some multiseeded fruits,
the extent to which the flesh develops is proportional to the number of
fertilized ovules.
[13] The pericarp is often differentiated into two or three distinct layers called the
exocarp (outer layer, also called epicarp),
mesocarp (middle layer), and
endocarp (inner layer). In some fruits, especially simple fruits derived from an
inferior ovary, other parts of the flower (such as the floral tube, including the
petals,
sepals, and
stamens), fuse with the ovary and ripen with it. In other cases, the sepals, petals and/or stamens and
style of the flower fall off. When such other floral parts are a significant part of the fruit, it is called an
accessory fruit.
Since other parts of the flower may contribute to the structure of the
fruit, it is important to study flower structure to understand how a
particular fruit forms.
[3]
There are three general modes of fruit development:
- Apocarpous fruits develop from a single flower having one or more separate carpels, and they are the simplest fruits.
- Syncarpous fruits develop from a single gynoecium having two or more carpels fused together.
- Multiple fruits form from many different flowers.
Plant scientists have grouped fruits into three main groups, simple fruits, aggregate fruits, and composite or multiple fruits.
[14] The groupings are not evolutionarily relevant, since many diverse plant
taxa may be in the same group, but reflect how the flower organs are arranged and how the fruits develop.
This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.
