Biology · Morphology of Flowering Plants · NEET
Aestivation is the arrangement of sepals or petals of the SAME whorl with respect to one another inside the flower bud. Phyllotaxy is the arrangement of LEAVES on the stem. Do not mix them. Aestivation is about the bud (before the flower opens); phyllotaxy is about leaves on the shoot. For NEET, remember aestivation describes calyx or corolla members touching or overlapping.
In valvate, the sepals or petals only TOUCH at their margins, with no overlapping (example: Calotropis). In twisted, one margin of each petal OVERLAPS the margin of the next petal, and this overlap goes in ONE regular direction all around (examples: china rose, cotton, lady's finger). So valvate = just touching, twisted = overlapping in a fixed direction.
Both twisted and imbricate have overlapping margins, so students confuse them. In twisted, the overlap follows ONE regular direction (each petal overlaps the next one in the same way). In imbricate, the overlap is IRREGULAR - one petal is fully outside, one is fully inside, and the rest overlap without a fixed pattern (examples: Cassia, gulmohar). Rule: twisted = regular one-way overlap; imbricate = irregular overlap.
Vexillary (also called papilionaceous) aestivation is seen in the pea and bean family (Fabaceae - Papilionoideae). There are five petals: the largest is the standard (vexillum), which overlaps two lateral petals called wings, and the two wings overlap the two smallest petals that together form the keel. Examples: Pisum sativum (pea), bean. This pattern is a special NEET favourite because it pairs with diadelphous stamens.
It can be about BOTH. Aestivation is the mode of arrangement of members of any one whorl - so it describes the sepals of the calyx or the petals of the corolla. In NEET questions the example usually points to petals (cotton, pea), but the definition covers sepals too. So do not assume it is only petals.
Calotropis shows VALVATE aestivation. Its petals just touch each other at the margins without any overlapping. Calotropis is the standard NCERT example of valvate, and NEET has directly asked this. Remember: Calotropis = Valvate.
In Calotropis, aestivation is:
Which one of the following plants shows vexillary aestivation and diadelphous stamens?
Match List I (A. Rose, B. Pea, C. Cotton, D. Mango) with List II (I. Twisted aestivation, II. Perigynous flower, III. Drupe, IV. Marginal placentation).
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Valvate, twisted, imbricate and vexillary. Valvate = margins just touch (Calotropis). Twisted = overlap in one regular direction (cotton, china rose). Imbricate = irregular overlap (Cassia, gulmohar). Vexillary = pea flower pattern with standard, wings and keel.
Calotropis is the standard NCERT and NEET example of valvate aestivation. Its petals only touch at the margins without overlapping.
Yes. Vexillary aestivation is also called papilionaceous. It is the corolla arrangement of the pea and bean family, with the largest petal (standard/vexillum) overlapping the wings, which overlap the keel.
Twisted has a regular one-way overlap (each petal overlaps the next in the same direction). Imbricate has an irregular overlap - one petal fully outside, one fully inside, no fixed pattern. Twisted = regular, imbricate = irregular.
NEET asks aestivation almost every year, often through direct examples (Calotropis, cotton, pea) or in match-the-column questions. Knowing the exact plant example for each type lets you answer these one-mark questions quickly and correctly.
