Aestivation - The Floral Arrangement

Definition Of Aestivation

Aestivation in botany is the arrangement that petals and sepals are assigned to and held in before the opening of a flower bud. The said arrangement before opening is most of the time of huge importance in relation to the developments received by the flower and the performance of its function. Botanists use it to identity and classify the plant species into different categories.

The botanists will have a knowledge of the flower aesthetics to understand the evolutionary interrelationships between different plant species. It also helps in the correct identification of plants, which becomes very important in botanical studies, horticulture, and agriculture. Patterns of aestivation affect the reproductive success of plants through their effects on how flowers interact with pollinators and in protecting their reproductive organs.

Types Of Aestivation

Aestivation has been classified into numerous types based on the part's arrangement on a flower bud. The commonly known types are valvate, twisted, imbricate, and quincuncial aestivation.

Valvate Aestivation

• Valvate aestivation, the edges of petals or sepals, is seen to barely touch each other, showing no overlapping.

• It is the least differentiated and most simple type in which the floral parts remain plaits along with each other.

Examples

• Hibiscus, Family Malvaceae are some common examples belonging to the valvate aestivation category.

• This is a common pattern in members of the Malvaceae family.

Twisted Aestivation

• In this the petals or sepals are overlapping each other, but in a methodical spiral manner.

• Each petal or sepal folds over the next one in a regular sequence, so that it overlaps in a one-way twist.

Examples

• In the Malvaceae, such as cotton and hibiscus, usually have twisted aestivation.

• China rose (Hibiscus rosa-sinensis) - is one of the common examples.

Imbricate Aestivation

• In this, the petals or sepals will overrun one another and result in irregular overlapping.

• There is no definite pattern of overlap, and the arrangement seems haphazard.

Examples

• Cassia and Gulmohar (foliage: Delonix regia) belonging to the Fabaceae family exhibit imbricate aestivation.

• This kind is common in many plants belonging to the leguminous species.

Vexillary Aestivation

• Vexillary aestivation is a mixture of imbricate and valvate; in the sense, there are both overlapping and touching margins.

• Generally, any two petals or sepals overlap, two are overlapped, and one portion is external.

Examples

• Solanaceae family, such as Solanum and Datura.

• Aestivation also occurs in the family Brassicaceae.

Biological Importance Of Aestivation

Aestivation is of great importance in varied biological processes, mainly in the reproduction and evolution of plants.

Pollination factor

• An appropriate type of aestivation may popularise easy penetration of the pollen or other parts of the flower by the vectors of the pollens so that healthy pollination occurs.

• Specific aestivation type attracts specific kind of pollens vectors; this result in species-specific pollination.

Protection Of Reproductive Parts

• It helps protect sensitive reproductive organs—stamen and pistils, from environmental stress and damage.

• Overlapping patterns may shade reproductive parts from too much sunlight, pests, and other harmful elements.

Evolutionary Significance

Aestivation patterns present adaptive advantages, which are the reflective evolutionary changes in plant species.

Adaptive Advantages

• Pollination mechanisms are improved with specialized floral arrangements.

• The reproductive parts are better protected and have increased chances of successful reproduction.

Examples Of Evolutionary Changes

• Transition from primitive to advanced aestivation in some plant families.

• Adaptation to various pollinators and environmental conditions and diversification over the period result in varied floral structures found in species.

Aestivation In Different Plant Families

Aestivation patterns vary dramatically in different plant families, and each family presents unique characters.

Fabaceae

• It shows imbricate aestivation.

• It shows overlapping of petals or sepals without a specific pattern.

Examples

• Cassia, Gulmohar (Delonix regia).

Solanaceae

• Usually shows quincuncial aestivation.

• Combination of overlapping and touching edges.

Examples

• Solanum, Datura.

Brassicaceae

• Most of the species show quincuncial aestivation.

• Evolution of adaptive features of the floral structure to provide more protection and better pollination.

Examples

• Mustard, Brassica, Cabbage, Brassica oleracea.