5. MORPHOLOGY OF FLOWERING PLANTS
THE FRUIT
-
It is a ripened ovary developed
after fertilisation.
-
It is a characteristic feature of the
flowering plants.
-
A fruit formed without fertilisation of
the ovary is called parthenocarpic fruit.
-
In mango & coconut, fruit is called a
drupe. They are one seeded and
develop from monocarpellary superior ovaries.
-
A fruit consists of
o Pericarp (fruit wall): It may be dry or fleshy.
Thick and fleshy pericarp is differentiated
into outer epicarp, middle mesocarp and inner endocarp.
o Seeds
- In mango, the pericarp is well
differentiated into thin epicarp, fleshy edible mesocarp and stony hard
endocarp.
-
In coconut, the mesocarp is fibrous.
THE SEED
-
It is the mature ovule developed after fertilisation.
- A seed is made up of a seed coat and an embryo.
-
Embryo is made up of a radicle, an
embryonal axis and one (e.g. wheat, maize) or 2 cotyledons (e.g. gram
& pea).
Structure of a Dicotyledonous Seed
-
The outermost covering of a seed is the
seed coat.
-
Seed coat has 2 layers: outer testa and
inner tegmen.
- On the seed coat, there is a scar called hilum
through which the developing seeds are attached to the fruit.
-
Above the hilum is a small pore called
the micropyle.
 Structure
of dicotyledonous seed |
-
Within the seed coat is the embryo,
consisting of an embryonal axis and two cotyledons.
- The cotyledons are often fleshy and full
of reserve food materials. At the two ends of the embryonal axis, the radicle
and plumule are present.
- In some seeds such as castor, the endosperm
is formed due to double fertilisation. It is a food storing tissue.
- In plants such as bean, gram and pea, the
seeds are non-endospermous (endosperm is not seen in mature seeds).
Structure
of Monocotyledonous Seed
-
Generally, monocot seeds are endospermic
but some are non-endospermic (e.g. orchids).
- In cereals such as maize, the seed coat
is membranous and generally fused with the fruit wall.
- The endosperm is bulky and stores food.
- The outer covering of endosperm separates
the embryo by a protein layer called aleurone layer.
- The embryo is small and situated in a
groove at one end of the endosperm. It consists of one large and shield shaped
cotyledon known as scutellum and a short axis with a plumule and
a radicle.
- The plumule is protected in a sheath called coleoptile and radicle is protected in a sheath called coleorhiza.
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by gaurav s.k
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