Types of Inflorescence — Revision Notes

⚡ 30-Second Revision

Inflorescence: — Arrangement of flowers on floral axis.
Racemose (Indeterminate): — Main axis grows indefinitely, flowers acropetal (youngest at apex).

* Raceme: Pedicellate flowers (Mustard). * Spike: Sessile flowers (Amaranthus). * Spadix: Fleshy spike with spathe (Maize, Colocasia). * Catkin: Pendulous spike, unisexual (Mulberry). * Corymb: Flat-topped, lower pedicels longer (Candytuft). * Umbel: Flowers from one point, umbrella-like (Coriander). * Capitulum (Head): Flattened receptacle, sessile florets (Sunflower).

Cymose (Determinate): — Main axis terminates in flower, flowers basipetal (oldest at apex).

* Monochasial: One lateral branch (Scorpioid: Cotton; Helicoid: Heliotropium). * Dichasial: Two lateral branches (Jasmine, Dianthus). * Polychasial: More than two lateral branches (Calotropis).

Special Types:

* Hypanthodium: Flask-shaped receptacle, internal flowers (Fig). * Verticillaster: False whorl of dichasial cymes (Ocimum, Salvia). * Cyathium: Cup-shaped involucre, 1 female, many male flowers (Euphorbia).

2-Minute Revision

Inflorescence refers to the arrangement of flowers on the floral axis. It's broadly categorized into Racemose, Cymose, and Special types. Racemose inflorescences are characterized by an indefinitely growing main axis, with flowers arranged in acropetal succession (youngest at the top).

Key examples include Raceme (mustard, pedicellate flowers), Spike (amaranthus, sessile flowers), Spadix (maize, fleshy spike with spathe), Catkin (mulberry, pendulous spike), Corymb (candytuft, flat-topped), Umbel (coriander, umbrella-like), and Capitulum (sunflower, flattened receptacle with florets).

Cymose inflorescences have a main axis that terminates in a flower, leading to definite growth and basipetal succession (oldest at the top). Subtypes include Monochasial (e.g., cotton - scorpioid, Heliotropium - helicoid), Dichasial (jasmine, two lateral branches), and Polychasial (Calotropis, multiple lateral branches).

Special types are highly modified, such as Hypanthodium (fig, flask-shaped receptacle), Verticillaster (Ocimum, false whorl of cymes), and Cyathium (Euphorbia, cup-shaped involucre mimicking a single flower).

Remember the growth pattern of the main axis and the succession of flowers as primary distinguishing features.

5-Minute Revision

Inflorescence, the arrangement of flowers on the floral axis, is crucial for plant reproduction. It's classified based on the main axis's growth and flower arrangement.

Racemose Inflorescence (Indeterminate): The main axis continues to grow, and flowers develop laterally in an acropetal succession (youngest at apex, oldest at base). This allows for prolonged flowering.

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Raceme: — Elongated peduncle, pedicellate flowers (e.g., Mustard, Radish).
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Spike: — Elongated peduncle, sessile flowers (e.g., Amaranthus, Achyranthes).
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Spadix: — Fleshy peduncle, sessile flowers, enclosed by a large bract called a spathe (e.g., Maize, Colocasia).
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Catkin: — Pendulous spike, often unisexual, falling off after fruiting (e.g., Mulberry, Willow).
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Corymb: — Short peduncle, lower flowers have longer pedicels, bringing all flowers to the same level (e.g., Candytuft, Cauliflower).
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Umbel: — Short peduncle, all pedicellate flowers arise from a single point, forming an umbrella shape. Often has an involucre of bracts (e.g., Coriander, Carrot). Compound umbels have umbellets (e.g., Fennel).
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Capitulum (Head): — Flattened receptacle, densely packed sessile florets, surrounded by an involucre (e.g., Sunflower, Marigold).

Cymose Inflorescence (Determinate): 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).

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Monochasial Cyme: — One lateral branch below the terminal flower.

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

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Dichasial Cyme: — Two lateral branches below the terminal flower (e.g., Jasmine, Dianthus).
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Polychasial Cyme: — More than two lateral branches below the terminal flower (e.g., Calotropis, Nerium).

Special Types of Inflorescence: Unique, highly modified forms.

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Hypanthodium: — Fleshy, hollow, flask-shaped receptacle with an apical ostiole, bearing unisexual flowers internally (e.g., Fig, Peepal).
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Verticillaster: — Two condensed dichasial cymes at each node, forming a false whorl (e.g., Ocimum, Salvia).
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Cyathium: — Cup-shaped involucre with nectar glands, enclosing a single female flower and many male flowers (each a single stamen), mimicking a single flower (e.g., Euphorbia).

Focus on understanding the defining features and memorizing key plant examples for each type for NEET.

Prelims Revision Notes

Types of Inflorescence: NEET Quick Recall

I. Racemose Inflorescence (Indeterminate/Indefinite Growth)

Main Axis: — Continues to grow indefinitely.
Flower Arrangement: — Acropetal succession (youngest at apex, oldest at base).
Examples & Key Features:

* Raceme: Pedicellate flowers on elongated peduncle. *Ex: Mustard, Radish.* * Spike: Sessile flowers on elongated peduncle. *Ex: Amaranthus, Achyranthes.* * Spadix: Fleshy spike, enclosed by a spathe (large bract).

*Ex: Maize, Colocasia, Banana.* * Catkin: Pendulous, often unisexual spike. *Ex: Mulberry, Willow, Oak.* * Corymb: Short peduncle, lower flowers with longer pedicels, forming a flat top. *Ex: Candytuft, Cauliflower.

* * Umbel: Short peduncle, all pedicellate flowers from one point, umbrella-like. Often has involucre. *Ex: Coriander, Carrot, Cumin.* (Compound Umbel: Fennel, Dill). * Capitulum (Head): Flattened receptacle, dense sessile florets (ray & disc), involucre.

*Ex: Sunflower, Marigold, Zinnia.

II. Cymose Inflorescence (Determinate/Definite Growth)

Main Axis: — Terminates in a flower, limiting growth.
Flower Arrangement: — Basipetal succession (oldest at apex, youngest at base).
Examples & Key Features:

* Monochasial Cyme (Uniparous): One lateral branch below terminal flower. * Helicoid: Branches on same side, coiled. *Ex: Heliotropium, Hamelia.* * Scorpioid: Branches alternately, zigzag. *Ex: Cotton, Ranunculus.* * Dichasial Cyme (Biparous): Two lateral branches below terminal flower. *Ex: Jasmine, Dianthus, Bougainvillea.* * Polychasial Cyme (Multiparous): More than two lateral branches below terminal flower. *Ex: Calotropis, Nerium.*

III. Special Types of Inflorescence

Hypanthodium: — Fleshy, hollow, flask-shaped receptacle with ostiole, internal unisexual flowers. *Ex: Fig (Ficus species).*
Verticillaster: — Two condensed dichasial cymes at each node, forming a false whorl. *Ex: Ocimum (Tulsi), Salvia, Leucas.*
Cyathium: — Cup-shaped involucre (fused bracts) with nectar glands, enclosing one female flower (pistil) and many male flowers (stamens). Mimics single flower. *Ex: Euphorbia pulcherrima (Poinsettia), Euphorbia hirta.*

Vyyuha Quick Recall

To remember the main Racemose types: Really Smart Students Can Catch Umbrellas Happily.

Raceme
Spike
Spadix
Catkin
Corymb
Umbel
Head (Capitulum)