🌼 Inflorescence – Definition
A flower is a modified shoot. The shoot apical meristem changes to a floral meristem, causing the axis to condense and the internodes to stop elongating.
Inflorescence is the arrangement and distribution of flowers on the floral axis (peduncle). It is a key feature for plant identification and classification.
🌿 Types of Inflorescence
Based on whether the apex continues to grow or terminates in a flower, inflorescences are divided into two main types: Racemose and Cymose.
🌸 1️⃣ Racemose Inflorescence
- The main axis (peduncle) continues to grow indefinitely.
- The flowers are borne laterally on the axis.
- The arrangement of flowers is in an acropetal succession: the oldest flowers are at the base of the axis, and the youngest flowers are at the top (apex).
- Growth: Indeterminate.
- Examples: Mustard, Radish, Lupin.
Common Types of Racemose Inflorescence:
| Type | Description | Example |
|---|---|---|
| Raceme | Flowers with pedicels along main axis | Radish, Mustard |
| Spike | Sessile flowers on elongated axis | Achyranthes |
| Catkin | Pendant spike with unisexual flowers | Mulberry |
| Corymb | Lower pedicels longer, forming flat top | Candytuft (Iberis) |
| Umbel | Pedicels arise from same point | Onion |
| Head (Capitulum) | Sessile flowers on flat receptacle | Sunflower, Marigold |
🌹 2️⃣ Cymose Inflorescence
- The main axis terminates in a flower, hence the growth is limited.
- The flowers are borne in a basipetal succession: the oldest flower is at the top (terminating the main axis), and the younger flowers develop from lateral buds below it.
- Growth: Determinate.
- Examples: Jasmine, Calotropis, Solanum, Bougainvillea.
Common Types of Cymose Inflorescence:
| Type | Description | Example |
|---|---|---|
| Uniparous (Monochasial) Cyme | Main axis ends in a flower, one lateral branch continues growth | Jasmine, Drosera |
| Biparous (Dichasial) Cyme | Main axis ends in a flower, two branches continue growth | Ixora |
| Multiparous (Polychasial) Cyme | Main axis gives rise to many branches | Calotropis |
🌸 3️⃣ Special Types of Inflorescence
| Type | Description | Example |
|---|---|---|
| Verticillaster | Cluster of sessile flowers in whorls | Ocimum (Tulsi) |
| Cyathium | Cup-shaped inflorescence with a central female flower surrounded by male flowers | Euphorbia |
| Hypanthodium | Fleshy receptacle enclosing flowers | Ficus (Fig) |
🌺 Importance of Inflorescence Study
- Helps in identification and classification of plants.
- Indicates evolutionary advancement of flowers.
- Crucial for floral formula and diagram interpretation.
💡 Questions and Answers
Q1. Define inflorescence.
A1. Inflorescence is the arrangement of flowers on the floral axis or peduncle.
Q2. Differentiate between racemose and cymose inflorescence.
A2. Racemose: indefinite axis, acropetal succession; Cymose: definite axis, basipetal succession.
Q3. Give one example of special inflorescence.
A3. Euphorbia (cyathium type) or Ficus (hypanthodium type).
Q4. What is meant by acropetal succession of flowers?
A4. Acropetal succession is a pattern of flower arrangement where the flowers open in sequence from the base of the inflorescence axis towards the apex. This means the oldest, most mature flowers are at the bottom, and the youngest buds are at the top. This is characteristic of Racemose inflorescences.
Q5. What is meant by basipetal succession of flowers?
A5. Basipetal succession is a pattern of flower arrangement where the first flower to open is the terminal one at the apex of the inflorescence axis. Subsequent, younger flowers develop from lateral buds below the terminal flower. This means the oldest flower is at the top, and the youngest are at the base. This is characteristic of Cymose inflorescences.
Q6. Give two examples each for racemose and cymose inflorescence.
A6.
- Racemose: Mustard, Radish (also Lupin, Amaranth).
- Cymose: Jasmine, Calotropis (also Solanum, Bougainvillea).