Aestivation (botany)

Aestivation or estivation is the positional arrangement of the parts of a flower within a flower bud before it has opened. Aestivation is also sometimes referred to as praefoliation or prefoliation, but these terms may also mean vernation: the arrangement of leaves within a vegetative bud.

Aestivation can be an important taxonomic diagnostic; for example Malvaceae flower buds have valvate sepals, with the exception of the genera '' Fremontodendron'' and '' Chiranthodendron'', which have sometimes been misplaced as a result.

Terminology

The terms used to describe aestivation are the same as those used to describe leaf vernation.

Classes of aestivation include:
* ''crumpled''
* '' decussate''
* ''imbricate'' – overlapping
** ''contorted'' or ''twisted'' – every petal or sepal is outside its neighbour on one margin, and inside its neighbour on the other margin.
*** ''cochleate'' – spirally twisted.
*** ''contortiplicate'' – contorted and also plicate.
** ''quincuncial'' – with five parts, where two petals or sepals are outside all others, two are inside all others, and the fifth is outside on one margin and inside on the other.
* ''induplicate'' – folded inwards.
* ''open'' – petals or sepals do not overlap or even touch each other .
* ''reduplicate'' – folded outwards.
* ''valvate'' – margins of adjacent petals or sepals touch each other without overlapping.
* ''vexillary'' – a special type of aestivation occurring in plants like pea; in this type of aestivation a large petal called ''standard'' encloses two smaller petals.

References

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Plant morphology

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