Question

Descending imbricate aestivation occurs in the corolla of
A. Tamarinds
B. Cassia
C. Pisum
D. Helianthus

Answer 1

Hint: We know that it is the whole whorl of petals. For the matter of fact, we also know that in descending imbricate aestivation the one unpaired petal present at the posterior overlaps the lateral petals.

Complete Answer:
- In the given question we need to find which of the structures has the descending imbricate aestivation present in them.
- In imbricate aestivation, one petal is completely inside and one is completely outside. The remaining perianth members show one edge inside and the other edge outside and are divided into two types descending imbricate and ascending imbricate.
- In descending imbricate aestivation, the posterior petal overlaps one margin of the two lateral petals.
- Tamarind shows imbricate aestivation.
- In case of cassia ascending imbricate aestivation is seen.
- In the case of Pisum we know that descending imbricate aestivation is there which means it has one posterior standard petal, two lateral wings and two fuse petals called as keel. This can make it the correct option.
- So, helianthus or sunflower does not show descending imbricate aestivation which again eliminates it from being the correct option.

So, the correct option is C as it fulfills all the criteria of the descending imbricate aestivation.

Note: Aestivation is the mode of arrangement of sepals or petals in the floral bud with respect to the other members of the same whorl.