Question

What is aestivation? Describe various types of aestivation.

Answer 1

In Botany, the mode of the configuration of sepals or petals of a bud-like plant is indeed an Aestivation. Aestivation is also sometimes referred to as prefoliation or prefoliation, but these terms can also imply vernation: the distribution of leaves within a vegetative bud.

Complete answer: Aestivation in plants can be specified as the perianth array (a common term for sepals and petals) inside a floral bud. It is important to understand the taxonomy of plants, wherein flowers of different groups demonstrate distinctive aestivation. For instance, the sepals and petals of the Hibiscus flowers belonging to the Malvaceae family show valve and twisted aestivation, nevertheless.
The different aestivation forms are just as follows: Imbricate, overlapping perianth sections:
(i) Convoluted or contorted, imbricate with perianth aspects of a single whorl intervening at one margin, overlying at the other, as in the corolla of several Malvaceae; folded, wrinkled, particularly in buds.
(ii) Imbricate-alternate, imbricate with an outer whorl of the perianth parts (sepals or outer tepals) contrasting with the inner whorl of the perianth parts (petals or inner tepals).
(iii) Quincuncial, imbricate with perianth aspects of a single pentamerous whorl having two members overlapping at both margins and overlapping only at one margin.
(iv) Valvate, with a bundle of perianth-parts gathering at the margins, not overlapping.
(v) Involute, valve for each perianth-part unfolding
Additional Information:
The aestivation is a collection of perianth members, i.e., sepals and petals with regards to each other. This is one of the variables which can be used to distinguish flowers based on the form of aestivation. The calyx plus corolla is the outer edge whorl, i.e. the perianth. In only certain plants, sepals and petals are observed to be auxiliary whorls, or we can say they are quasi-differentiated. The outermost whorl, i.e. perianth, would've been called polyphyllus if the sepals and petals stay independent, as in the flowers of Gloriosa superba. But if sepals and petals are found to be intertwined as in the flowers of Polianthes tuberosa, then the perianth is called gamophyllous.

Note: Aestivation is among the floral properties that articulate the arrangement of calyx and corolla in a floral bud relative to each other. Calyx and corolla could be called perianth descriptively. Thus, aestivation simply displays the perianth array, comprising sepals and petals.