Types of Aestivation in Corolla – Class 11 | Chapter – 5 | Short Notes Series PDF

Types of Aestivation in Corolla: Aestivation in Plants is the arrangement of petals and sepals in floral buds before blooming. It is arranged with respect to the other members of the whorl. The term aestivation is often confused with vernation which basically refers to the arrangement of new leaves and scales in a leaf bud. The petals and sepals are collectively termed perianth. The arrangement of perianth inside a flower bud before it blooms is known as the aestivation of plants.

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Types of Aestivation in Corolla

The positional organization of petals and sepals are of the following types – valvate aestivation, twisted aestivation, imbricate aestivation, vexillary aestivation and quincuncial aestivation. 

Valvate Aestivation

Valvate is open aestivation that includes flowers whose petals and sepals are only attached through the margins of a single whorl by leaving a free space within them. 

  • The petals and the sepals of the whorl do not overlap each other.
  • They meet at the edges, therefore valvate aestivation is referred to as open aestivation.
  • The edges of the corolla and calyx are really close within a whorl of a flower but they do not intersect each other.
  • Example: Mustard, Annona and Calotropis flower

Twisted Aestivation

Twisted Aestivation is also known as convolute or contorted aestivation. 

  • Twisted Aestivation includes the flowers whose petals or sepals are organized in a manner in which one edge overlaps the next edge inside. 
  • The other margin however is overlapped by the former petal or sepal edge.
  • Therefore, they overlap the neighbouring members on one side regularly. 
  • The overlapping can be regarded as clockwise or anticlockwise with regularity.
  • The edge of an appendage overlaps the next, which gives it a different or distorted shape. Therefore, it is called ‘twisted aestivation’. 
  • Example: Ladyfinger, Cotton, and Hibiscus flowers.

Imbricate Aestivation

In imbricate aestivation, the perianth or the outermost whorl includes petals and sepals that overlap each other in such a way that a few petals are inside entirely and some are entirely outside. 

  • The outermost whorl or perianth consists of petals which are either entirely inside or entirely outside. 
  • Therefore, the overlapping of corolla or calyx in imbricate aestivation does not occur in a specific position which means it has a non-specific structural arrangement.
  • The two sub-types of imbricate aestivation are ascending imbricate and descending imbricate aestivation.
  • Example: Flowers of Gulmohar.

Vexillary Aestivation

Vexillary aestivation is also known as descending imbricate or papilionaceous aestivation. 

  • The aestivation includes overlapping of the petals from the bottom of the posterior end towards the anterior side.
  • The overlapping starts from the posterior side and ends at the anterior side. 
  • This includes flowers having an intersection of the odd posterior petal and the margin of 2 lateral petals.
  • A pair of the smallest anterior petals are overlapped by the lateral wings or the petals.
  • Hence, in this arrangement of petals, the odd or the largest posterior petal is entirely on the outside.
  • The anterior pair of petals or the keel is on the inside.
  • The overlapping pattern in vexillary aestivation is in a descending manner. 
  • Example: Crotalaria, Dolichos, and Tephrosia flowers.

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