What type of aestivation is found in papilionaceous corolla (Fabaceae) where a large posterior standard petal overlaps two lateral wing petals, which in turn overlap two anterior keel petals?

Answer and explanation

Correct answer: B. Vexillary aestivation

- One large posterior petal (standard or vexillum),
- Two lateral petals (wings or alae),
- Two small anterior petals fused together (keel or carina).
  1. Step 1: Aestivation describes the arrangement of sepals or petals in the floral bud relative to other members of the same whorl.
  2. Step 2: In papilionaceous flowers (pea, bean), the corolla consists of 5 petals:
  3. Step 3: The standard overlaps the wings, which overlap the keel; this arrangement is termed vexillary (descending imbricate) aestivation.
Answer
Vexillary aestivation
Why not the others: 'Valvate aestivation' occurs when petals meet edge to edge without overlapping (e.g., Calotropis); 'Twisted aestivation' occurs when one margin of each petal overlaps that of the adjacent petal regularly in one direction (e.g., China rose, cotton); 'Imbricate aestivation' occurs when margins overlap irregularly without a fixed direction (e.g., Cassia, Delonix).

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