The mode of arrangement of sepals or petals in a floral bud is known as aestivation. Describe the various types of aestivation found in flowers.

(N/A) $\rightarrow$ The mode of arrangement of sepals or petals in a floral bud with respect to the other members of the same whorl is known as aestivation.
$\rightarrow$ The main types of aestivation are as follows:
$(i)$ Valvate: When sepals or petals in a whorl just touch one another at the margin, without overlapping, it is said to be valvate, e.g., $Calotropis$.
$(ii)$ Twisted: If one margin of the appendage overlaps that of the next one and so on, it is called twisted, e.g., China rose, lady's finger, and cotton.
$(iii)$ Imbricate: If the margins of sepals or petals overlap one another but not in any particular direction, the aestivation is called imbricate, e.g., $Cassia$ and Gulmohur.
$(iv)$ Vexillary: In pea and bean flowers, there are five petals; the largest (standard) overlaps the two lateral petals (wings), which in turn overlap the two smallest anterior petals (keel). This type of aestivation is called vexillary or papilionaceous.