Edunes Online Education
University: Rabindranath Tagore University (RTU), Hojai, Assam
Course: B.Sc. Botany (Honours)
Subject: Morphology, Embryology & Anatomy of Angiosperms (BOT-MAJOR-2)
Edunes Online Education
Week 3: INFLORESCENCE
Definition:
Inflorescence is the arrangement of flowers on the floral axis (peduncle).
It answers one core biological question:
How does a plant organize its reproductive units for maximum success?
Inflorescence is the arrangement of flowers on the floral axis (peduncle).
It answers one core biological question:
How does a plant organize its reproductive units for maximum success?
🧠 Think like a strategist:
A single flower is reproductive.
A cluster of flowers is reproductive efficiency multiplied.
Inflorescence = Architecture of reproduction.
A single flower is reproductive.
A cluster of flowers is reproductive efficiency multiplied.
Inflorescence = Architecture of reproduction.
1️⃣ RACEMOSE vs CYMOSE (Core Logic)
What is the FIRST thing you should observe when identifying inflorescence?
Observe the growth of the main axis.
The entire classification depends on ONE principle:
Does the main axis continue to grow or does it stop in a flower?
Does the main axis continue to grow or does it stop in a flower?
| Feature | Racemose | Cymose |
|---|---|---|
| Main Axis | Continues to grow | Ends in a flower |
| Growth Type | Indeterminate | Determinate |
| Flower Order | Acropetal (old → base) | Basipetal (old → top) |
🔹 A. Racemose Inflorescence
Main axis grows indefinitely.
Flowers develop in acropetal succession.
(Older flowers at base, younger at top)
Flowers develop in acropetal succession.
(Older flowers at base, younger at top)
🧠 Visual Model:
Imagine a tower under construction.
Lower floors are complete.
New floors keep getting added above.
Imagine a tower under construction.
Lower floors are complete.
New floors keep getting added above.
🌿 RACEMOSE → "Race goes on"
Growth never stops.
Growth never stops.
🔹 B. Cymose Inflorescence
Main axis terminates in a flower.
Growth becomes limited (determinate).
Growth becomes limited (determinate).
🧠 Visual Model:
The leader blooms first.
Once top flower forms, vertical growth stops.
Side branches continue.
The leader blooms first.
Once top flower forms, vertical growth stops.
Side branches continue.
🌸 CYMOSE → "Cycle stops at the top"
If the top flower is the oldest, what type is it?
Cymose (basipetal order).
2️⃣ SPECIAL INFLORESCENCES
Some plants modify their structure so cleverly that what appears as a single flower
is actually a highly organized cluster.
🔸 Cyathium
Cup-shaped structure.
One central female flower.
Many male flowers surrounding it.
One central female flower.
Many male flowers surrounding it.
🧠 Think of it as a "mini ecosystem in a cup".
Looks like one flower → Actually many.
Looks like one flower → Actually many.
CYATHIUM → Cup-like cluster.
🔸 Hypanthodium
Fleshy hollow receptacle.
Small opening (ostiole) at top.
Flowers are hidden inside.
Small opening (ostiole) at top.
Flowers are hidden inside.
🧠 Imagine a hollow ball with flowers lining the inside wall.
Outside looks simple.
Inside is complex.
Outside looks simple.
Inside is complex.
HYPANTHODIUM → Hidden flowers inside.
🔸 Verticillaster
Two condensed cymose clusters at a node.
Appears like a whorl.
Appears like a whorl.
🧠 Think symmetry.
Two clusters opposite each other → Looks circular.
Two clusters opposite each other → Looks circular.
VERTICILLASTER → Vertical whorl illusion.
3️⃣ Master Thinking Framework
🧠 Identification Algorithm:
Step 1 → Observe main axis growth.
Step 2 → Check order of flowering.
Step 3 → Look for structural modification (cup / hollow / whorl).
Step 1 → Observe main axis growth.
Step 2 → Check order of flowering.
Step 3 → Look for structural modification (cup / hollow / whorl).
When you understand growth behavior,
classification becomes pattern recognition — not memorization.
classification becomes pattern recognition — not memorization.
3️⃣ Field Activity
✔ Visit garden / campus flora.
✔ Observe flower arrangement carefully.
✔ Sketch and label peduncle, axis, and flower position.
✔ Observe flower arrangement carefully.
✔ Sketch and label peduncle, axis, and flower position.
While observing, ask yourself:
• Does the main axis keep growing?
• Which flowers are older — top or bottom?
• Is it appearing as a single flower but actually a cluster?
• Which flowers are older — top or bottom?
• Is it appearing as a single flower but actually a cluster?
4️⃣ Internal Evaluation – Spotting Test
Students may be asked to identify:
- Type of inflorescence
- Growth pattern (determinate/indeterminate)
- Order of flowering (acropetal/basipetal)
- Special structural modifications
🧠 Final Recall Framework:
Growth continues? → Racemose
Growth stops? → Cymose
Cup-like cluster? → Cyathium
Hollow structure? → Hypanthodium
False whorl? → Verticillaster
Growth continues? → Racemose
Growth stops? → Cymose
Cup-like cluster? → Cyathium
Hollow structure? → Hypanthodium
False whorl? → Verticillaster
Master the logic, not the list.
When you understand growth behavior, identification becomes automatic.
When you understand growth behavior, identification becomes automatic.
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