What is called Aestivation ? Describe its types.

$\rightarrow$ The mode of arrangement of sepals or petals in floral bud with respect to the other members of the same whorl is known as aestivation.

$\rightarrow$ Its types are as follow:

$(i)$ Valvate : When sepals or petals in a whorl just touch one another at the margin, without overlapping, is said to be valvate for 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, Cotton.

$(iii)$ Imbricate : If the margins of sepals or petals overlap one another but not in any other direction the aestivation is called imbricate for e.g. Cassia and Gulmohur.

$(iv)$ Vexillary or Papilionaceous : 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 this type of aestivation is called papilionaceous.