Question

What are the types of imbricate aestivation?

Answer 1

flower is a modified shoot, it has a long or short stalk called a pedicel. The upper part of the pedicel is swollen, which is called thalamus. Floral leaves are present on the thalamus. There are 4 types of floral leaves: 1.Sepal 2.Petal 3.Stamen 4.Carpel. The mode of arrangement of petals (also sepals) in a flower bud with respect to members of the same whorl is known as aestivation. It may be of the following types: Valvate, twisted or contorted, imbricate, Quincuncial, vexillary.

Complete answer:
Imbricate aestivation:
When both margins of the one petal are covered by the other two petals and both margins of another one cover the other. Rest are arranged in a twisted manner. Or if the margins of sepals or petals overlap one another but not in any particular direction, then it is known as imbricate aestivation.
Eg. Cassia , gulmohar.
There are 2 types of imbricate aestivation:
1. Descending imbricate or Vexillary or papilionaceous:
The posterior petal is outermost and largest and is known as standard or vexillum which overlaps the two lateral petals, wings or alae. These two lateral petals overlap two smallest anterior petals i.e. keel or carina. Vexillary arrangement is found in the pea family.
Eg. Pea, bean (papilionatae subfamily of leguminosae family).

2. Ascending imbricate:
The posterior petal is innermost, i.e. its both margins are overlapped by lateral petals.
Eg. Caesalpinioideae subfamily of leguminosae.

Note:
When the petals of a whorl lie adjacent to other petals and just touch one another at the margin without overlapping then it is known as valvate aestivation, e.g. Calotropis plant. When one margin of a petal covers adjacent petal and the other margin is covered by another petal, this is called twisted aestivation eg.cotton.In case of quincuncial, out of the five petals, two are completely internal, two are completely external and in the remaining petal one margins internal and the other margin is external. eg. Murraya.