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 Vernation (from ''vernal'' meaning ''spring'', since that is when leaves spring forth in temperate regions) is the formation of new leaves or fronds. In plant anatomy, it is the arrangement of leaves in a bud. In pine species, new leaves are short ...

: the arrangement of leaves within a vegetative bud. Aestivation can be an important taxonomic diagnostic; for example

Malvaceae Malvaceae, or the mallows, is a family of flowering plants estimated to contain 244 genera with 4225 known species. Well-known members of economic importance include okra, cotton, cacao and durian. There are also some genera containing familiar ...

flower buds have valvate sepals, with the exception of the genera ''

Fremontodendron ''Fremontodendron'', with the common names fremontia and flannelbush or flannel bush, is a genus of three known species of shrubs native to the Southwestern United States and northwest Mexico. Taxonomy They are within the botanical family Malv ...

'' and ''

Chiranthodendron ''Chiranthodendron'' is a flowering plant genus in the family Malvaceae. It comprises a single species of tree, ''Chiranthodendron pentadactylon''. Names The tree is called the devil's, monkey's or Mexican hand tree or the hand-flower in English ...

'', 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 Decussation is used in biological contexts to describe a crossing (due to the shape of the Roman numeral for ten, an uppercase 'X' (), ). In Latin anatomical terms, the form is used, e.g. . Similarly, the anatomical term chiasma is named aft ...

'' * ''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

+ Plant morphology {{botany-stub