Inflorescences

Dr. Babasaheb Ambedkar Marathwada university, Aurangabad, maharashtra, syllabus of B. Sc. Botany First year (Semester-I, paper-II

1. Inflorescences
Dr. ANJALI NAIK

2. Inflorescence- Specialized branch bearing flowers:
• Terminal inflorescence: In this case, the inflorescence
forms at the apex of main branches. Main axis con>nues
into axis of
Inflorescence Example: Foxglove ‘

• Axillary: In this case inflorescence forms on the branches.
Example: pea
• Solitary flower:
• Some flowers are solitary like rose. The solitary flowers
have large corolla to aGract insects. There are two forms of
solitary flowers

3. RECEMOSE INFLORESCENCE

• The main axis does not end in a
flower, but it grows con>nuously.
• Develops flowers on its lateral sides
in acropetal succession (i.e., the
lower or outer flowers are older than
the upper or inner ones).
• The various forms of racemose
inflorescence may be described
under three head
• (i) Main axis elongated, i.e., (a)
raceme; (b) spike; (c) spikelets; (d)
catkin and (e) spadix.
• (ii) Main axis shortened, i.e.,
(a) corymb and (b) umbel.
• (iii) Main axis flaCened, i.e.,
capitulum or head.

4. Subtypes of Racemose Inflorescence

5. Raceme
• The main axis remains elongated
and it bears laterally a number of
stalked flowers. The lower/ older
flowers possess longer stalks than
the upper or younger ones, e.g.,
radish (Raphanus sa>vus),
mustard (Brassica campestris),
etc.
• When the main axis of raceme is
branched and the lateral
branches bear the flowers, the
inflorescence is known as
compound raceme or panicle,
e.g., neem (Azadirachta indica),
gul-mohar (Delonix regia), etc.

6. SPIKE INFLORESCENCE
• Spike: The inflorescence
in which main axis is
elongated and bears
sessile lateral flowers is
called spike.
• The flowers may be
bracteate or
ebracteate. Example:
BoGle brush, ginger,
wheat,
WHEAT JOWAR

7. Spikelet
• Spikeletes are Spike
inflorescences with fewer
flowers
• Arranged in a spike
inflorescence which is
composed of several to
many spikelets which are
combined in various
manners on a main axis
called the rachis. Some
are in compound spikes
(i.e., in wheat—Tri>cum
aes>vum),

8. Catkin
• Catkin: This is a
modified spike with a
long and drooping axis
bearing unisexual
flowers, e.g., mulberry
(Moras alba), birch
(Betula spp.), oak
(Quercus spp.), etc.
• Catkin

9. Corymb
• In this inflorescence the
main axis remains
compara>vely short and
the lower flowers possess
much longer stalks or
pedicels than the upper
ones so that all the
flowers are brought more
or less to the same level,
e.g., in candytu\ (Iberis
amara).

10. Umbel
• The primary axis remains
compara>vely short, bears
at its >p a group of flowers
which possess pedicel of
almost equal lengths.
•  Flowers are seen to arise
out from a common point.
In this inflorescence a whorl
of bracts forming an
involucre is present,
•  Each individual flower
develops from the axil of a
bract.e.g. Coriander

11. Spadix
• The special type of
spike with main axis
thick and fleshy bearing
unisexual flowers is
called spadix.
• The large protec>ve
bract is known spathe.
• Example: Date palm,
arum.
• SPADIX

12. Head/capitulum
• The inflorescence in which main axis
flaGened to form receptacle and
flowers are crowed on it is called
capitulum.
• The flowers are small and sessile.
They are called florets.
• The young florets are present at the
centre of receptacle and older
flowers are present towards the
periphery.
• The receptacle has many overlapping
bracts at the base called involucre.
• The flowers May be bracteate or
ebracteate.
• HEAD/CAPITULUM

13. Descrip>on-Head/Capitulum
• The capitula may be
homogamous or heterogamous.
• Homogamous: In this case, all
flowers are of same kind.
Example: Sonchus

• Heterogamous: In this case, two
types of flowers are present in
the capi`la. Example: Sunflower.
Sunflower has two types of small
flowers, disc florets and ray
florets. The disc florets are
present in the central region.
They are tubular and bisexual. [he
ray florets are present towards
the periphery. They are pis>llate
or neuter.

14. Cymose Inflorescence
• In this type, the growth of the
main axis is ceased by the
development of a flower at its
apex.
•  The lateral axis which develops
the terminal flower also
culminates in a flower and its
growth is also ceased.
• The flowers may be pedicellate
(stalked) or sessile (without
stalk).
•  Flowers develop in basipetal
succession, i.e., the terminal
flower is the oldest and the
lateral ones younger. This type of
opening of flowers is known as
centrifugal.

15. Cymose subtypes
• (i) Uniparous or
monochasial cyme
a. Helicoid b.
Scorpioid
• (ii) Biparous or
dichasial cyme;
• (iii) Mul>parous or
polychasial cyme
and
• (iv) Cymose
capitulum.

16. Monochasial/Uniparous cyme

•  Main axis ends in a flower,produces
only one lateral branch at a >me
ending in a flower. The lateral and
succeeding branches again produce
only one branch at a >me like the
primary one.
(a) Helicoid Cyme: When the lateral axes
develop successively on the same side,
forming a sort of helix, the cymose
inflorescence is known as helicoid or
one-sided cyme, e.g., in Begonia, Juncus,.
(b) Scorpioid Cyme: When the lateral
branches develop on alternate sides,
forming a zigzag, the cymose
inflorescence is known as scorpioid or
alternate-sided cyme, e.g., (coGon).

17. Biparous/dichasial
• In this type the peduncle
bears a terminal flower
and stops growing.
•  The peduncle produces
two lateral younger
flowers or two lateral
branches that terminate
in a flower.
• There are three flowers;
the oldest in the centre.
• e.g., jasmine, teak, Ixora,
Saponaria, etc.

18. Polychasial/Mul>parous
• Main axis culminates in a
flower, and it again
produces lateral flowers
around. The oldest flower is
in the centre and ends the
main floral axis (peduncle).
This is a simple
polychasium.
• The whole inflorescence
looks like an umbel, but is
readily dis>nguished from
the laGer by the opening of
the middle flower first, e.g.,
Calotropis procera

19. SPECIAL TYPES
• In this inflorescence there is a
cup-shaped involucre, o\en
provided with nectar secre>ng
glands. The involucre encloses
a single female flower,
represented by a pis>l, in the
center, situated on a long
stalk.
• This female flower remains
surrounded by a number of
male flowers arranged
centrifugally. Each male flower
is reduced to a solitary stalked
stamen.
• E.g. Poinse'a
• CYATHIUM

20. Hypanthodium
• The receptacle forms a
hollow cavity with an apical
opening guarded by scales.
• Here the flowers are borne
on the inner wall of the
cavity.
•  The female flowers develop
at the base of the cavity and
the male flowers towards
the apical pore-orifice.
• The examples are found in
genus Ficus of Moraceae
• HYPANTHODI

21. VERTICILLASTER

• A condensed form of dichasial
cyme with a cluster of sessile or
sub-sessile flowers in the axil of a
leaf.
•  Forming a false whorl of flowers
at the node.
• The first of main floral axis gives
rise to two lateral branches and
these branches and the
succeeding branches bear only
one branch each on alternate
sides.
• The type of inflorescence is
characteris>c of Lamiaceae
(Labiatae) family. Typical
examples, are—Ocimum, Coleus,
Mentha, Leucas, etc.