Question

What is vexillum?

Answer 1

Flowers with the characteristic irregular and butterfly-like corolla seen in many, but not all, plants of the species-rich Faboideae subfamily of legumes are known as papilionaceous flowers (from Latin: papilion, a butterfly). Valerius Cordus, according to Tournefort, coined the title Flores papilionacei to describe the flower of the bean.

Complete answer:
The upper petal of a papilionaceous flower.
The flowers are bilaterally symmetrical, with five petals in the corolla. The banner refers to a single big top petal (also vexillum or standard petal). The banner's semi-circular base encompasses and compresses two equal and smaller lateral wings.

These have a vexillum present:- Papilionaceae. Vexillum In botany, the standard or large posterior petal of a papilionaceous flower. It is external and wrapped around the others in the bud.

Fabaceae, sometimes known as Papilionaceae, is a huge and commercially significant flowering plant family. Members of the Fabaceae family exhibit vexillary aestivation. The vexillum or standard, the outermost posterior petal, is large, two lateral petals are known as the wings or alae, and the two anterior and innermost petals are fused to form a boat-shaped structure known as the keel or carina in vexillary aestivation. As a result, vexillum is found in the Papilionaceae family.

The corolla of a papillionaceous flower is fashioned like a butterfly and has five petals. The standard or vexillum petal is the largest and most prominent. Wings or Alae are two little, free lateral petals that are overlapped by the posterior standard petal. The innermost boat-shaped structure covering the stamens and carpels of the flower is called Keel, and it is formed by fusing the two anterior petals. It has wings or alae that cover it. This form of arrangement is known as descending imbricate, and it may be found in Pea and Lathyrus.

Note:-
Aestivation means arrangement of accessory floral organs (sepals or petals) in relation to one another in a flower. Valvate aestivation occurs when the sepals or petals in a whorl are just touching. Twisted aestivation: One appendage's margin overlaps the next appendage's margin. Sepal or petal margins overlap but not in any specific orientation in imbricate aestivation.
Vexillary Aestivation is also a type of aestivation.