2. What is Inflorescence?
• A flower is a significant part of a plant tailored for reproduction. In addition, it is
an essential part of the bouquet, decorations, celebrations, garden, rituals,
etc. Among different parts of a plant, the flower is the most attractive part due
to its beauty and fragrance.
3. Types of Inflorescence
• In a plant, flowers may grow either as a single flower or as a group. The
inflorescence is defined as the arrangement of a cluster of flowers on a floral
axis. The inflorescence is of two types, they are: Racemose and Cymose
4. • Racemose Inflorescence
In this type of inflorescence, the flowers branch laterally on the floral
axis. Here the floral axis keeps on growing and the flowers develop in
an acropetal pattern.
Cymose Inflorescence
In this type of inflorescence, the flower is the terminating point of each
floral axis. In Cymose inflorescence, flowers follow the basipetal
pattern of growth.
5. Racemose type
Simple raceme – The pedicellate bisexual flowers are arranged
in an acropetal succession on an elongated peduncle. Example –
Crotalaria
6. • Spike – Similar to simple raceme except that the flowers are
sessile.Example – Achyranthes
7. • Compound Spadix – Unisexual male and female flowers sessile
flowers are arranged in acropetal succession. Example – Cocos
nucifera
8. • Capitulum – Inflorescence axis is flattened to form a receptacle
wherein ligulate ray florets and tubular disc florets develop in a
centripetal manner. Example – Tridax
10. • Helicoid cyme – Flowers are consecutively produced on one
side on the peduncle to give a helicoid appearance. Example –
Hamelia
11. • Dichasial – The peduncle ends up with a flower and two lateral
flowers are produced under the central flower one on each side
for a cluster of three flowers to be formed. Example –
Jasminum.
12. • Polychasial cyme- Same pattern of development of flowers as
seen in dichasial additionally it is continued here. Centrifugal
mode of development. Example – Calotropis
13. What is Placentation?
The ovules remain attached to the inner wall of the ovary to a
parenchymatous outgrowth or cushion called the placenta. The
mode of arrangement of ovules within the ovary is called
placentation.
Funiculi connect the ovules present in the flower’s ovary. The
Placenta is the part of the ovary where the funiculus is attached.
14. Types of Placentation in Flower
The arrangement of seed in a fruit depends on the type of
placentation. There are different types of placentation:
15. 1. Marginal
a) In this type of placentation, the gynoecium is monocarpellary
(consisting of one carpel) and unilocular (one-chambered).
B) This type of placentation is mostly found in the family
Leguminosae or Fabaceae.
C) Examples of this placentation are: Pea, Gram, Mung, etc.
16. 2. Parietal
a) In this type of placentation, the gynoecium is polycarpellary (consisting of two or
more carpels) formed by fusing two or more carpels with their margins.
B) Carpels are united to form only one chamber.
C) Placentae are seen on the inner surface of the ovary, at the junctions of the
carpels.
D) Sometimes, the one-chambered becomes two-chambered by the developing of
a false septum or replum.
E) This type of placentation is found in mustard, Argemone and other members of
the Brassicaceae family.
17. 3. Axile
a) In this type of placentation, the gynoecium is polycarpellary, syncarpous (united).
B) The ovary is many chambered, and the number of chambers corresponds to the
number of carpels.
C) The placentae arise from the central axis. So, it is called axile placentation.
D) This type of placentation is found in Petunia (bilocular), Asphodelus (trilocular),
China-rose (pentalocular), Althaea (multilocular), tomato, lemon, etc. This is one of
the most common types of placentations in plants.
18. 4. Free Central
a) In this type of placentation, the gynoecium is polycarpellary.
B) The partition walls are found in the early stage of the ovary forming
chambers which are later being dissolved, the ovary becomes
unilocular.
C) Septa are absent.
D) Only one swollen placenta bearing a few ovules is borne at the
centre of the ovary, which is quite separate from the ovary wall.
E) This type of placentation is found in Dianthus, Primula, etc.
19. 5. Basal
a) In this type of placentation, the gynoecium is polycarpellary.
B) The ovary is unilocular.
C) A single ovule develops at the base of the ovary.
D) The placenta is placed on the tip of the thalamus at the floor of the
ovary.
E) This type of placentation is found in the members of the family
Asteraceae (sunflower family) and Poaceae (grass family).
F) Examples of this placentation: sunflower, rice, wheat, maize, etc.
20. 6. Superficial
a) In this type of placentation, the gynoecium is polycarpellary,
syncarpous and multilocular.
B) The placentae develop all around the inner surface of the
partition walls and many ovules are borne on the placentae
without any specific order.
C) This type of placentation is found in Nymphaea (Waterlily) and
mainly in the Nymphaeaceae family.
21. Significance
The significance of placentation is:
a) It helps in the transfer of nutrients, respiratory gases, and
water from maternal tissue to the developing embryo.
B) It protects the developing ovules.
C) It also helps in the elimination of waste from the embryo.
22. What is the Seed?
A seed is a basic part of any plant. The ovules after fertilization,
develop into seeds. A seed is made up of a seed coat and an
embryo. The embryo is made up of a radicle, an embryonal axis
and one (wheat, maize) or two cotyledons (gram and pea). A
seed is found inside a fruit which converts into a new plant when
we plant it. Hence, the seed is the most important part.
23. Types of Seeds
A Seed is primarily of two types. The two types are:
1. Monocotyledonous Seed
2. Dicotyledonous Seed
24. Structure of a Monocotyledonous Seed
A Monocotyledonous seed, as the name suggests, has only one cotyledon.
There is only one outer layering of the seed coat. A seed has the following
parts:
Seed Coat: In the seed of cereals such as maize, the seed coat is membranous
and generally fused with the fruit wall, called Hull.
Endosperm: The endosperm is bulky and stores food. Generally,
monocotyledonous seeds are endospermic but some as in orchids are non-
endospermic.
Aleuron layer: The outer covering of endosperm separates the embryo by a
proteinous layer called aleurone layer.
25. Embryo: The embryo is small and situated in a groove at one
end of the endosperm.
Scutellum: This is one large and shield-shaped cotyledon.
Embryonal axis: Plumule and radicle are the two ends.
Coleoptile and coleorhiza: The plumule and radicle are
enclosed in sheaths. They are coleoptile and coleorhiza.
26. Structure of a Dicotyledonous Seed
Unlike monocotyledonous seed, a dicotyledonous seed, as the name
suggests, has two cotyledons. It has the following parts:
Seed coat: This is the outermost covering of a seed. The seed coat
has two layers, the outer testa and the inner tegmen.
Hilum: The hilum is a scar on the seed coat through which the
developing seed was attached to the fruit.
Micropyle: It is a small pore present above the hilum.
Embryo: It consists of an embryonal axis and two cotyledons.
27. Cotyledons: These are often fleshy and full of reserve food
materials.
Radicle and plumule: They are present at the two ends of the
embryonal axis.
Endosperm: In some seeds such as castor, the endosperm
formed as a result of double fertilisation, is a food storing tissue.
In plants such as bean, gram and pea, the endosperm is not
present in the matured seed. They are known as non-
endospermous.
