Question

Margins of sepals or petals overlap one another but not in any particular direction. This type of aestivation is called:

• A. Valvate
• B. Twisted
• C. Vexillary
• D. Imbricate

Hint:

Quick Revision of Aestivation: Valvate \(\rightarrow\) Touch but do not overlap Twisted \(\rightarrow\) Overlap in one direction Imbricate \(\rightarrow\) Overlap irregularly Vexillary \(\rightarrow\) Papilionaceous flowers (Pea)

Answer 1

The Correct Option is D

Concept: Aestivation refers to the arrangement of sepals or petals in a floral bud with respect to other members of the same whorl. Different types of aestivation are important taxonomic characters and are frequently used in plant identification. Major types include:
• Valvate
• Twisted
• Imbricate
• Vexillary

Step 1: Understand valvate aestivation.
In valvate aestivation: \[ \text{Margins touch each other} \] but \[ \text{Do not overlap} \] Example: Calotropis.

Step 2: Understand twisted aestivation.
In twisted aestivation: \[ \text{Each petal overlaps the next} \] in a regular direction. One margin remains outside and the other remains inside. Example: Hibiscus.

Step 3: Understand vexillary aestivation.
This is a specialized form found in papilionaceous flowers. There are:
• Standard petal
• Wing petals
• Keel petals Example: Pea.

Step 4: Understand imbricate aestivation.
In imbricate aestivation: \[ \text{Margins overlap one another} \] but \[ \text{There is no fixed directional pattern} \] This is exactly the condition described in the question.

Step 5: Match the definition with the option.
The statement says: \[ \text{``Margins overlap one another but not in any particular direction.''} \] This is the textbook definition of: \[ \boxed{\text{Imbricate Aestivation}} \]