Botany - Morphology of Flowering Plants Question with Solution | TestHub

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. The main types of aestivation are valvate, twisted, imbricate and vexillary.
In valvate, sepals or petals just touch one another at the margin, without overlapping,e.g., Calotropis.
In twisted, one margin of sepal or petal overlaps that of the next one and so on, e.g., China rose, lady’s finger, cotton, etc.
In imbricate, The margins of sepal or petals overlap one another but not in any particular direction e.g., Cassia,Goldmohur.
In vexillary, the largest posterior petal (vexillum or standard) overlaps two lateral petals (alae or wings) which in turn overlaps the two smallest, anterior but united petals (keel or carina),e.g., pea, bean etc.