Inflorescence — Revision Notes

⚡ 30-Second Revision

Inflorescence: — Arrangement of flowers on floral axis.
Racemose: — Indefinite growth, acropetal succession (youngest at apex).

- Examples: Raceme (*Mustard*), Spike (*Amaranthus*), Spadix (*Maize*), Catkin (*Mulberry*), Corymb (*Candytuft*), Umbel (*Coriander*), Capitulum (*Sunflower*).

Cymose: — Definite growth, basipetal succession (oldest at apex).

- Examples: Monochasial (Helicoid: *Heliotropium*; Scorpioid: *Cotton*), Dichasial (*Jasmine*), Polychasial (*Calotropis*).

Special Types:

- Cyathium: Cup-shaped involucre, single female, many male flowers (*Euphorbia*). - Verticillaster: Condensed dichasial cymes in leaf axils (*Ocimum*). - Hypanthodium: Fleshy, hollow receptacle, flowers on inner surface (*Ficus*).

2-Minute Revision

Inflorescence is the organized arrangement of flowers on a plant's floral axis, crucial for reproduction. It's broadly categorized into Racemose, Cymose, and Special types. Racemose inflorescences are characterized by indefinite growth of the main axis and acropetal succession of flowers (youngest at top, oldest at base).

Key examples include the simple raceme of mustard, the spike of amaranthus, the fleshy spadix of maize, the head-like capitulum of sunflower, and the flat-topped corymb of candytuft. Cymose inflorescences, conversely, have definite growth, where the main axis terminates in a flower, and subsequent flowers develop from lateral branches in basipetal succession (oldest at top, youngest at base).

Subtypes include monochasial cymes (helicoid in *Heliotropium*, scorpioid in cotton), dichasial cymes (jasmine), and polychasial cymes (*Calotropis*). Special types like cyathium (*Euphorbia*), verticillaster (*Ocimum*), and hypanthodium (*Ficus*) exhibit highly modified structures.

Understanding these types and their specific plant examples is vital for NEET.

5-Minute Revision

Inflorescence, the specific arrangement of flowers on the floral axis (peduncle), is a key morphological feature influencing pollination and reproductive success. The two primary classifications are Racemose and Cymose, based on the growth pattern of the main axis and the sequence of flower development.

Racemose Inflorescence: The main axis grows indefinitely, never terminating in a flower. Flowers are borne laterally in acropetal succession (youngest at apex, oldest at base). Examples:

Raceme: — Pedicellate flowers on an unbranched peduncle (e.g., Mustard, Radish).
Spike: — Sessile flowers on an unbranched peduncle (e.g., Amaranthus, Achyranthes).
Spadix: — Fleshy spike covered by spathe (e.g., Maize, Colocasia).
Catkin: — Pendulous spike, unisexual flowers (e.g., Mulberry, Oak).
Corymb: — Lower flowers with longer pedicels, all flowers at same level (e.g., Candytuft, Cauliflower).
Umbel: — All pedicellate flowers from a single point (e.g., Coriander, Carrot).
Capitulum (Head): — Flattened receptacle with sessile florets in centripetal succession, surrounded by involucre (e.g., Sunflower, Marigold).

Cymose Inflorescence: The main axis terminates in a flower, limiting its growth. Subsequent flowers arise from lateral branches in basipetal succession (oldest at apex, youngest at base).

Monochasial Cyme: — One lateral branch per axis.

* Helicoid: Branches on one side, forming a coil (e.g., *Heliotropium*, Hamelia). * Scorpioid: Branches alternately on opposite sides, zigzag (e.g., Cotton, Ranunculus).

Dichasial Cyme: — Two lateral branches per axis (e.g., Jasmine, Dianthus, Bougainvillea).
Polychasial Cyme: — More than two lateral branches per axis (e.g., *Calotropis*, *Euphorbia*).

Special Types of Inflorescence: Unique modifications.

Cyathium: — Cup-shaped involucre with single female flower (pistil) and many male flowers (stamens) (e.g., *Euphorbia* species like Poinsettia).
Verticillaster: — Two axillary dichasial cymes condensed into a false whorl (e.g., *Ocimum* (Tulsi), *Salvia*).
Hypanthodium: — Fleshy, hollow receptacle with an apical ostiole, bearing flowers on its inner surface (e.g., *Ficus* species like Fig, Banyan).

For NEET, focus on the defining characteristics of each type and, most importantly, memorize the classic plant examples associated with them. Distinguish clearly between acropetal and basipetal succession and the growth patterns of the main axis.

Prelims Revision Notes

Inflorescence is the arrangement of flowers on the floral axis. It's a key feature in plant morphology for NEET.

I. Racemose (Indefinite/Indeterminate) Inflorescence:

Main Axis Growth: — Indefinite, continues to grow.
Flower Succession: — Acropetal (youngest at apex, oldest at base).
Flower Opening: — Centripetal (periphery to center) in capitulum, or base to apex.
Types & Examples:

* Raceme: Pedicellate flowers. Ex: Mustard (*Brassica*), Radish (*Raphanus*), Gulmohar. * Spike: Sessile flowers. Ex: Achyranthes, Amaranthus, Bottle Brush. * Spadix: Fleshy spike, covered by spathe.

Ex: Maize (female), Colocasia, Arum, Banana. * Catkin: Pendulous spike, unisexual. Ex: Mulberry, Oak, Birch. * Corymb: Lower pedicels longer, flowers at same level. Ex: Candytuft (*Iberis*), Cauliflower.

* Umbel: Pedicellate flowers from one point, often with involucre. Ex: Coriander, Cumin, Carrot. * Capitulum (Head): Flattened receptacle, sessile florets, centripetal. Ex: Sunflower, Marigold, Zinnia.

Compound Racemose (Panicle): — Branched raceme. Ex: Rice, Wheat, Grape.

II. Cymose (Definite/Determinate) Inflorescence:

Main Axis Growth: — Definite, terminates in a flower.
Flower Succession: — Basipetal (oldest at apex, youngest at base).
Flower Opening: — Centrifugal (center to periphery) or apex to base.
Types & Examples:

* Monochasial Cyme (Uniparous): One lateral branch. * Helicoid: Branches on one side (coil). Ex: *Heliotropium*, Hamelia, Drosera. * Scorpioid: Branches alternately (zigzag). Ex: Cotton (*Gossypium*), Ranunculus, Freesia. * Dichasial Cyme (Biparous): Two lateral branches. Ex: Jasmine (*Jasminum*), Bougainvillea, Dianthus. * Polychasial Cyme (Multiparous): More than two lateral branches. Ex: *Calotropis*, *Euphorbia*.

III. Special Types:

Cyathium: — Cup-shaped involucre, single female flower (pistil), many male flowers (stamens). Ex: *Euphorbia* (Poinsettia).
Verticillaster: — Two axillary dichasial cymes forming false whorls. Ex: *Ocimum* (Tulsi), *Salvia*, Leucas.
Hypanthodium: — Fleshy, hollow receptacle with ostiole, flowers on inner surface. Ex: *Ficus* (Fig, Banyan, Peepal).

Key Terms: Peduncle (main stalk), Pedicel (flower stalk), Bract (modified leaf at base of flower/inflorescence), Rachis (main axis of spike/compound inflorescence), Sessile (without pedicel).

NEET Focus: Memorize examples for each type. Understand the core differences between racemose and cymose (growth, succession). Pay extra attention to special types.

Vyyuha Quick Recall

To remember the special inflorescence types and their examples:

Curious Violets Hide Every Outstanding Flower

Curious: Cyathium -> Every: Euphorbia
Violets: Verticillaster -> Outstanding: Ocimum
Hide: Hypanthodium -> Flower: Ficus