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The Collaborative International Dictionary
AEstivation

AEstivation \[AE]s`ti*va"tion\, n.

  1. (Zo["o]l.) The state of torpidity induced by the heat and dryness of summer, as in certain snails; -- opposed to hibernation.

  2. (Bot.) The arrangement of the petals in a flower bud, as to folding, overlapping, etc.; prefloration.
    --Gray.

Wiktionary
aestivation

n. 1 (context biology English) A state of inactivity and metabolic depression during summer: the summer version of hibernation. 2 (context botany English) The arrangement (vernation) of the parts of a flower inside a bud; prefloration. 3 (context obsolete English) The spending or passing of a summer.

WordNet
aestivation
  1. n. (zoology) cessation or slowing of activity during the summer; especially slowing of metabolism in some animals during a hot or dry period [syn: estivation]

  2. (botany) the arrangement of sepals and petals in a flower bud before it opens [syn: estivation]

Wikipedia
Aestivation

Aestivation or æstivation (from , summer, but also spelled estivation in American English) is a state of animal dormancy, similar to hibernation, characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions. It takes place during times of heat and dryness, the hot dry season, which are often the summer months.

Invertebrate and vertebrate animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation. Both terrestrial and aquatic animals undergo aestivation.

Organisms who aestivate appear to be in a fairly "light" state of dormancy, as their physiological state can be rapidly reversed, and the organism can quickly return to a normal state. A study done on Otala lactea, a snail native to parts of Europe and Northern Africa, shows that they can wake from their dormant state within ten minutes of being introduced to a wetter environment. Fossil records show that the act of aestivating may be several hundred million years old.

The primary physiological and biochemical concerns for an aestivating animal are to conserve energy, retain water in the body, ration the use of stored energy, handle the nitrogenous end products, and stabilize bodily organs, cells, and macromolecules. This can be quite a task as hot temperatures and arid conditions may last for months. The depression of metabolic rate during aestivation causes a reduction in macromolecule synthesis and degradation. To stabilize the macromolecules, aestivators will enhance antioxidant defenses and elevate chaperone proteins. This is a widely used strategy across all forms of hypometabolism. These physiological and biochemical concerns appear to be the core elements of hypometabolism throughout the animal kingdom. In other words, animals who aestivate appear to go through nearly the same physiological processes as animals that hibernate.

Aestivation (botany)

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. 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.

lilacs 01.JPG|Lilac ( Syringa vulgaris), valvate aestivation aestivation.jpg|Phlox ( Phlox paniculata), contorted aestivation minor aestivation.jpg| Vinca minor, contorted aestivation Glory Photo.jpg| Ipomoea, contortiplicate aestivation 070302-5063 Merremia tuberosa.jpg|The corolla of Merremia tuberosa was contortiplicate in the bud

Usage examples of "aestivation".

Once the habitats were complete and moved into orbit around the destination planet, the Festival travelers would emerge from aestivation, ready to trade and listen.

He had dwelt here in the Scarlet Pylon, alone with his memories amid the ruins of his people, until the coming of Sarchimus, who discovered him during a period of slumber or aestivation, when he was virtually helpless.