Aestivation (botany)

Aestivation (or estivation in American English) refers to the mode of arrangement of the petals or sepals in a flower bud before it opens. This botanical term is significant in plant morphology, as it can provide insights into the evolutionary adaptations of plants and help in the identification and classification of species. Aestivation is comparable to phyllotaxis, which deals with the pattern of leaf arrangement in plants.

Types of Aestivation

There are several types of aestivation, each with its unique arrangement and significance. These include:

• Valvate Aestivation: In this type, the petals or sepals are arranged in a manner where they meet at the edges without overlapping. An example can be seen in the flowers of the genus Annona.

• Imbricate Aestivation: Here, the petals or sepals overlap each other like tiles on a roof. This type can be further divided into:
  • Twisted Aestivation: Each petal or sepal overlaps the next one at one edge and is overlapped on the other edge. Lathyrus and Rosa (roses) are examples.
  • Convolute Aestivation: One side of each organ is covered, and the other side covers the adjacent organ, seen in the Magnolia genus.

• Quincuncial Aestivation: This is a form of imbricate aestivation where there are five parts, with two entirely inside, two entirely outside, and one with one edge in and the other out. The Camellia genus exhibits this pattern.

• Cochleate Aestivation: A spiral arrangement, somewhat rare, seen in some members of the family Fabaceae.

• Contorted Aestivation: Similar to twisted aestivation but with a more pronounced spiral arrangement. It is observed in the Convolvulaceae family.

Function and Significance

Aestivation patterns can protect the reproductive parts of the flower from environmental stressors such as heat, cold, and desiccation. The arrangement can also play a role in the efficiency of pollination, as the structure of the bud can influence the accessibility of pollen and nectar to pollinators.

In taxonomy and phylogenetics, the type of aestivation can be a crucial characteristic for identifying plant species and understanding their evolutionary relationships. It provides insights into the developmental biology of plants, showing how genetic and environmental factors influence the morphology of flowers.

See Also

• Flower
• Sepal
• Petal
• Plant morphology
• Phyllotaxis
• Pollination