Structure and development of fruit- Development botany

1. STRUCTURE AND
DEVELOPMENT OF FRUIT

2. Fruit
• A seed-bearing structure found in flowering
plants or also called angiosperms is known as
fruit.
• It is formed from the ovary present in the seed
after flowering in a plant takes place.
• Fruits have great agricultural output and some
of these have acquired symbolic and cultural
significance .

3. Fruit Structure
A fruit consists of an important structural
component called pericarp.
Pericarp:
It is the outer layer which is often edible
and is formed from the ovary and it surrounds
the seeds.

4. In some species, in addition to this portion,
other tissues can form the edible portion as well.
The pericarp, further, consists of the following
structures:
• Epicarp: It is the outermost layer of pericarp.
• Mesocarp: It is the middle layer of pericarp.
• Endocarp: It is the innermost layer of pericarp.
(The sweet juicy and edible flesh is the
mesocarp, the inner most hard covering is the
endocarp. These three layers are not easily
distinguishable in dry fruits.)

5. The fruits are usually classified into three
groups, namely simple, aggregate and multiple
or composite fruits.

6. Simple fruits
When a single fruit develops from a single
ovary of a single flower, it is called simple fruit.
The ovary may be monocarpellary or
multicarpellary syncarpous.
On the nature of pericarp, simple fruits are
divisible into two types
i) Fleshy fruits and
ii) Dry fruits

7. Simple fleshy fruits
In these fruits either the entire pericarp or part of
the pericarp is succulent and juicy when fully ripe.
Normally the fruit wall may be differentiated into
three layers - an outer epicarp, a middle mesocarp and
an inner endocarp. As a general rule, the fleshy fruits are
indehiscent.
Fleshy fruits are broadly divided into two
kinds, baccate and drupaceous. Baccate fruits are fleshy
fruits with no hard part except the seeds. Berry is
an example for the first category while drupe falls under
the second type.

9. 1. Berry: It is a many seeded fruit. Here the epicarp is thin,
the mesocarp and endocarp remain undifferentiated. They
form a pulp in which the seeds are embedded. In these fruits,
all parts including the epicarp with the seeds are edible
eg. Tomato
2. Drupe:
This is normally a one-seeded fruit. In these fruits the
pericarp is differentiated into an outer skinny epicarp, a
middle fleshy and juicy mesocarp and an inner hard and stony
endocarp. Drupes are called stone fruits because of the stony
hard endocarp.
The endocarp encloses Follicle a single seed. The
edible portion, i. Basifixed (Innate): Filament is attached to
the base of the anther (eg. Brassica) of the fruit is the fleshy
mesocarp eg. mango. In coconut, the mesocarp is fibrous, the
edible part is the endosperm.

10. 3. Hesperidium:
It is a skind of baccate fruit that develops from a
superior multicarpellary and syncarpous ovary.
The fruit wall is differentiated into three layers - an
outer glandular skin or epicarp, a middle fibrous
mesocarp, and an inner membranous endocarp.
The latter divides the fruit chamber into a number
of compartments.
The seeds arise on axial placentae and are covered
by juicy hairs or outgrowths from the lacentae that are
edible.
It is characteristic fruit of the genus Citrus (Fam.
Rutaceae)

11. 4. Pepo: A large fleshy fruit developing from a
tricarpellary, syncarpous, unilocular and inferior
ovary with parietal placentation. The fruit is many
seeded with pulpy interior; eg. Cucumber, Melon,
Bottle gourd etc.
5. Pome: It is a fleshy and a false fruit or
Pseudocarp. It develops from a multicarpellary
syncarpous inferior ovary in which the receptacle
also develops along with the ovary to become
fleshy and enclosing the true fruit. The true fruit
containing seeds remains inside. The edible part is
fleshy thalamus. eg. Apple, Pear etc.

12. Simple Dry Fruits
These fruits have dry pericarp, which is not
distinguished into three layers. The dry simple fruits
are further divided into three types-
Dehiscent- Legume, Follicle, Capsule
Schizocarpic - Lomentum, Cremocarp, Regma
Indehiscent- Achene, Caryopsis, Nut

13. Aggregate fruit
An aggregate fruit develops from a single
flower, with multicarpellary, apocarpous,
superior ovaries and each of them develops into
simple fruitlets.
An aggregate fruit, therefore consists of a
collection of simple fruits as in Polyalthia. The
carpels of the flower unite and give rise to a
single fruit as in Annona squamosa.

14. Multiple or Composite Fruit
Multiple or composite fruit is formed by all the flowers of a
whole inflorescence grouped together to give a single big fruit. In a
sense, multiple fruits are false fruits.
In Jack, the type of multiple fruit is sorosis. The rachis and all
the floral parts of the female inflorescence fuse together forming
composite fruit. The inflorescence axis and the flowers all become
fleshy.
In the centre of the fruit, there is a club-shaped, thick, fleshy
central axis, which is the inflorescence axis. The edible part of the fruit
represents the perianth, which is fleshy and juicy. The pericarp is bag-
like and contains one seed. The spines on the tough rind represent the
stigmas of the carpel. The sterile or unfertilized flowers, occur in the
form of numerous, elongated, whitish, flat structures in between the
edible flakes.

15. 3 Modes of Fruit Development
1. Apocarpous fruit development from a single
flower with one or more separate carpels;
these are the simplest form of fruits.
2. Syncarpous fruit development from a single
gynoecium with two or more carpels that are
fused together.
3. Multiple fruits that rise from multiple
flowers.

16. Development of a Fruit
The maturation of one or more flowers results in the formation of a
fruit and it is the gynoceium of the flower that forms all or some parts
of the fruit.
1. One or more ovules inside the ovary was fount in the egg cells are
present in megagametophyte.
2. These ovules become seeds after double fertilization.
3. The ovules are then fertilized in a process starting with pollination.
4. Pollination is the movement of the pollen from the stamens to the
stigma of the flowers.
5. After pollination, the pollen leads to the growth of a tube through
the stigma into the ovary to the ovule. Further, two sperms are
transferred to the megagametophyte from the pollen.
6. Then, a zygote formation takes place with the unison of one of the
sperms with the egg within the megagametophyte.

17. 7. The second sperm then enters the central cell and forms
the endosperm mother cell, thus, completing the double
fertilization process.
8. Later, embryos of the seed are formed via zygote and the
endosperm mother cell gives rise to the endosperm which
is a nutritive tissue used by the embryo.
9. As the seeds develop into ovules, the ovary begins to ripen
and the pericarp (ovary wall) may become fleshy (such as in
berries or drupes) or a hard outer covering (such as in
nuts).
10. The pericarp differentiates into 2 or 4 distinct layers
known as the exocarp or epicarp, mesocarp and endocarp.

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