Different types of Aestivation in Flower

The arrangement of floral appandages such as sepals and petals in a flower bud  with respect to other member of the same whorl in flower is called  aestivation.The various type of aestivation are as follows-

Open aestivation -The adjacent petals lie well apart from one another. For example Mustard. 

Valvate aestivation - Petals are in contact on the margin without overlapping for Example-  Calotropis Apple

Twisted aestivation - In this type of Aestivation, one margin of petal regularly overlaps the margin of adjacent Petal. For Example China rose, cotton, lady finger 

Imbricate  estivation - There is an irregular overlapping of petals.This type of aestivation is of four types - Imbricate proper, quincuncial, ascending imbricate and descending imbricate.

Imbricate proper aestivation is present in Murraya in which a well defined pattern is absent.  In Quincuncial aestivation, two Petals  overlap adjacent  petal on their margin, two petals  get overlapped on the margin while one petal is overlapped  on one margin and overlapping on the other petal.

Ascending imbricate - The posterior  patel is the innermost. It is being overlapped on the margin  by the lateral petal. The lateral petals are in turn overlapped by anterior petals. For example

Cassia,Gulmohar

Descending imbricate or papilionaceous or vexillary Aestivation - In Pea  and Bean flower, there are five petals. The largest petal is called standard which overlaps the two lateral petals called wings which in turn overlap the two smallest anterior petals  called keel. This type of aestivation  is known as Descending imbricate or papilionaceous or vexillary Aestivation.