Denifition: Inflorescence
An Inflorescence is a cluster of flowers produced by a plant and carried on a specific reproductive axis. The “Peduncle” refers to the main axis of the inflorescence. The pedicel is the name given to the flower’s stalk. A bract is a leaf-like structure that contains a flower or inflorescence. ‘Bracteate’ refers to a flower with bracts, while ‘Ebracteate’ refers to a flower without them. ‘Bracteolate’ refers to flowers having bracteoles, whilst ‘ebracteolate’ refers to flowers without bracteoles. “Bracteoles” refers to the flower and the Bract. ‘Bracteolate’ refers to a flower having bracteoles, while ‘Ebracteolate’ refers to a flower without them.
INFLORESCENCE TYPES
The inflorescence is divided into two categories.
They are of two types:
1) Racemose or indefinite.
2) Definite or Cymose
1.Indefinite racemose inflorescence
Racemose Inflorescence has the following features:-
A. The peduncle is also known as “indefinite growth” since it continues to expand.
B. The peduncle does not end in a flower.
C. Flowers are grouped in an acropetal pattern. Older flowers are at the base of the stem, while younger blossoms are at the tip.
D. Flowers open in a ‘Centripetal’ order, meaning the lower (marginal) blooms in the inflorescence are older and open first, while the central flowers open later.
Racemose Inflorescence Types:
The Racemose inflorescence is further divided into the forms listed below. The following are some of them:-
A. Simple Raceme: In this kind, an elongated Peduncle bears acropetal Pedicillate flowers. Cassia
B. Spike: The extended peduncle of this kind holds sessile flowers in an Acropetal way.E,g Acyranthus
C. Compound Raceme: It’s called a “Compound Raceme” or “Panicle” when the Peduncle is branched and each branch contains Pedicillate blooms in an acropetal fashion. E,g Mango
D.Spadix: The peduncle of this species is thick and fleshy, and it contains sessile unisexual flowers. The spathe is a single big colorful bract that surrounds the entire flower. Colocasia is a good example. It’s called “Compound Spadix” when the Axis of Spadix is branched, each branch bearing unisexual flowers, and the entire fluorescence is covered by a big woody, boat-shaped bract. E,g Musa, and Coconut.
E. Corymb: Peduncle is short in this kind. Lower flower pedicels are much longer than upper flower pedicels, ensuring that all flowers are roughly at the same level. For example, Gold mohur.
F. Umbel: The peduncle is greatly condensed in this kind, and the blooms have similar length pedicels that emerge from the same spot. The involucre is formed by bracteate flowers with bracts grouped in a whorl at the base. Onion is a good example. It’s called a “Compound Umbel” when the main axis is branched and the branches are of equal size, and it contains flowers with pedicels like an Umbel. E,g Carrot and coriander
G. Capitulum or Head: It is the Compositae family’s distinctive inflorescence ( Asteraceae).In this type, the Peduncle is flattened to form a circular disc known as the Receptacle. It has a huge amount of green bracts forming an Involucre on its lower surface. The flowers are grouped in a centripetal pattern on the receptacle. The central blooms are younger, while the peripheral flowers are older, and the flowering sequence goes from the periphery to the center.
Florets are the sessile tiny blooms. The periphery Zygomorphic Ray florets and the central, actinomorphic ‘Disc florets’ are the two types of Florets.
An inflorescence can be classified into two types based on the type of florets present:-
1) Homogamous head – Only one type of Floret in the head inflorescence.
2) Heterogamous head: Inflorescence with both Ray and Disc florets.
II. Cymose Inflorescence or Definite type:-
The Cymose Inflorescence has the following characteristics:
1. The peduncle ends in a flower.
2. The blooms are placed in a Basipetal pattern, with the older petals at the top and the younger blossoms at the bottom.
3. Flowers open in a ‘Centrifugal’ order, meaning that the older central flowers open first and the younger periphery flowers open later, while the central flowers are younger and open later.
CYMOSE INFLORESCENCE TYPES
1. The Lone cyme: The peduncle of a solitary cyme ends in a single bloom.e,g Hibiscus
2. Uniparous or Monochasial cyme: The primary axis of this kind ends in a flower. The plant then grows one lateral branch in the axil of a bract, which likewise produces a bloom. There are two basic types of flowers based on their development.
Helicoid cyme and Scorpioid cyme are the two types.
a) Helicoid cyme: This type of cyme develops successive branches on the same side, producing a helix. Hamelia is a good example.
b) Scorpioid cyme: This kind develops successive lateral branches from bracts on opposing sides of the axes, resulting in a Zigzag pattern. E,g Heliotropium
3. Dichasial Cyme: In this kind, the main axis finishes in a flower, and behind it, two flowers emerge from axils of oppositely positioned bracts. Jasmine, for example. Dichasium is formed from these diverse chemicals, as in Clerodendron, Ixora.
4. Polychasial Cyme: In this kind, the main axis terminates in a flower, followed by the development of more than two lateral branches, each of which behaves identically. E,g Calotropois, for example.
III. MULTIPLE INFLORESCENCE:
‘Mixed type’ inflorescences have characteristics of both Racemose and Cymose inflorescences. Thyrsus has an indefinable Peduncle that produces flowers in a cymose cluster in an acropetal fashion, similar to Raceme. E,g Ocimum sanctum (Tulsi-Basil).
IV.SPECIAL INFLORESCENCE
Along with its distinctive traits, Special Inflorescence may display Racemose or Cymose characteristics.
It is divided into three categories, which are as follows:
A.Cyathium 2. Hypanthodium 3. Verticillaster
1. Cyathium: A specialized cymose inflorescence, Cyathium is a specialized cymose inflorescence. The involucre is cup-shaped, generated by the fusion of bracts. It has a disc-like axis with a single pistillate bloom (female flower) in the center with a long pedicel that extends out of the cup. Many staminate flowers (Male flowers) are grouped in a Zig-Zag pattern around them. The Nector gland, a honey-secreting disc, is located on one side of the cup. E,g Euphorbia
2. Hypanthodium: The peduncle of Hypanthodium condenses into a fleshy, cup-shaped receptacle with an entrance known as the “Ostiole.” The receptacle has a hollow chamber in which unisexual flowers grow. Male flowers are found at the ostiole, whereas female flowers are found near the base. There are sterile Goll blooms in between these two.
3. Verticillaster: The unique inflorescence of the Lamiaceae family is Verticellaster.Biparous cyme occurs in the axils of opposing leaves in this kind, and lateral branches generate Uniparous Scorpioid cyme. Flowers are sessile and form a vertical false whorl around the stem.