Aestivation (botany)

A diagram showing some kinds of petal or sepal aestivation in flower buds. A: quincuncial; B,C: cochleate; D: contorted; E: valvate; F: open.

Aestivation or estivation refers to 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.

The terms used to describe aestivation are the same as those used to describe leaf vernation.^[1] Classes of aestivation include:

• 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
• crumpled
• decussate
• 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.

• 
  Lilac (Syringa vulgaris), valvate aestivation
• 
  Phlox (Phlox paniculata), contorted aestivation
• 
  Vinca minor, contorted aestivation
• 
  Ipomoea, contortiplicate aestivation
• 
  The corolla of Merremia tuberosa was contortiplicate in the bud

References