What are the types of imbricate aestivation?

Imbricate aestivation describes the overlapping arrangement of petals or sepals in a flower bud before it opens. The term aestivation refers to how floral parts are folded or arranged in the bud stage. In imbricate aestivation, some petals are partially inside or outside others, resembling roof tiles. There are three main types:

1. Quincuncial – In a five-petaled flower, two petals are completely inside, two are completely outside, and one is partly covered on one side and partly covers on the other. Example: Cassia.
2. Descending imbricate (Vexillary) – The largest petal (standard) overlaps the two lateral ones (wings), which in turn overlap the two smallest (keel) petals. Common in pea and bean flowers.
3. Ascending imbricate – The smallest petal is outermost and each successive petal overlaps the next. Example: Hibiscus.

This arrangement protects delicate floral organs during development and influences pollination by guiding insects. Botanists study aestivation patterns to identify plant families and understand floral evolution. Imbricate aestivation shows how plant structures adapt for reproduction and survival.