Whorls

In botany, we can say that a whorl is a circular type arrangement of parts of a plant for example leaves or flowers that wrap up around a point on a particular axis (vertical). A complete leaf whorl typically consists of a minimum of three elements. However, a pair of leaves emerging from the opposite side is not a whorl. 

Studying, the morphology of most flowers also known as cyclic flowers is mainly based on four types of whorls (the calyx, the corolla, the androecium, and the gynoecium). The flower which lacks any of these morphological floral parts is termed an incomplete or imperfect flower. In a variety of flowers, they are lacking the whorl, since due to that reason these parts are then spirally arranged instead. 

• For example- these types of arrangements are seen in the family Magnoliaceae. 
• Plants species consisting of very small internodes and some other genera such as Gallium, Nerium, Elodea, etc are found to be fairly rare for leaves to grow in whorls. 
• In some trees such as Brabejum stellatifolium and other similar species in the family Proteaceae a part of the genus Banksia, leaf whorls are often seen in these types of trees.

The four types of whorls on which the morphology of most flowers are based are as follows –

1. The calyx, none or multiple whorls of sepals at the base.
2. The corolla, none or multiple whorls of petals above the calyx.
3. The androecium, none or multiple whorls of stamens, each consisting of a filament and an anther.
4. The gynoecium: none or multiple whorls of carpels, each comprising of an ovary, a style, and also a stigma.

The Calyx 

A calyx is a plural form of a collection of sepals. A calyx is a part of the flower of angiosperms also called flowering plants. Calyx typically functions to protect the flower present in the bud, and often as support for the petals when they are in transition of blooming. The calyx is also known as the outermost whorl of parts that form a complete flower.

The word calyx was mainly derived from the Latin calyx, not to be confused with (Calix) which means ‘cup or goblet’. The calyx is derived from the Greek meaning ‘bud, calyx, husk, wrapping’ while Calix is derived from Greek  ‘cup, goblet’, and the words have been used conversely in botanical Latin.

After the whole process of flowering is completed, the calyx comes of no use anymore so it withers or becomes vestigial. However, in some plants, the calyx is still needed in the form of thorny calyx which is either dried or alive as a form of protection for the fruit or the seeds. 

Examples of these types of plants consisting of thorny calyx include species of Acaena, some of the Solanaceae such as the Tomatillo, Physalis philadelphica, and the water caltrop, Trapa natans. Morphologically we can say that both sepals and petals are modified leaves in another form. The calyx or the sepals and the corolla or the petals are the outer infertile whorls of the flower, which together form what we call perianth.

The Corolla

The corolla or the petals are the modified version of leaves also in whorls that usually surround the reproductive parts of flowers. In appearance, they are often seen as brightly coloured or in some unusual shape to mainly attract the pollinators. 

The collection of all of the petals of a flower is known as the corolla. Sepals or calyx are the other set of modified leaves that usually accompanies the petals, the sepals are collectively formed just beneath the corolla. The two flowering parts, the corolla, and the Calyx together form the perianth (perianth is also known as the non-reproductive part of a flower). 

In rare cases, when both sepals and petals of flowers are formed in such a way that it is nearly impossible to distinguish between those two, that’s when they are collectively known as the tepals.

Genera such as Aloe and Tulipa are examples of plants where the term tepals is observed. However, genera such as Rosa and Phaseolus have well-distinguished sepals and petals. When the undifferentiated tepals are seen as petals, they are named “petaloid”, as in petaloid monocots which means orders of monocots with brightly coloured tepals.

The Androecium

Androecium (another type of whorls) in other words is explained as the collection of stamens. The stamen is the reproductive organs of a flower that is mainly responsible for producing pollen grains. The reproductive organ of the flower typically consists of a stalk called the filament and an Anther that contains microsporangia. Anthers are most commonly two-lobed, anthers are mainly attached at the base or in the middle portion of the anther. 

The connective (an extension of the filament consisting of conducting strands) is known as the sterile tissue between the lobes. The connective is mainly seen as an extension on the backside of the anther. The microspore is responsible for the development of the pollen grains, the microspore is present in the microsporangium which contains the male gametophyte.

The androecium mainly consists of as low as one-half stamen meaning a single locule as usually in Canna species or as many as 3,482 stamens which have been counted in the saguaro (Carnegiea gigantea).

The Gynoecium

The word Gynoecium is derived from Ancient Greek which means ‘woman’, ‘female’, and is most commonly used as a collective term for the parts of a flower that are responsible for the production of ovules and ultimately help in developing into the fruit and seeds. 

The innermost whorl of a flower is the gynoecium, a gynoecium composed of pistils and is surrounded by the reproductive organs that are responsible for pollen-producing, the stamens collectively known as androecium. We often hear about the “female” portion of the flower, which simply refers to the gynoecium because it is capable of producing the female gametes known as the egg cells. 

Conclusion

So what do we know now: what are the 4 types of whorls? The 4 different types of whorls we studied are the Calyx, the corolla, the androecium, and the gynoecium. All these 4 floral parts are appointed to different functions such as to provide protection and also to produce both male and female gametes. Flowers whose petals are distinguishable I,e are not fused are known as polypetalous. 

The most known type of fusion between whorls mainly involves stamens and sepals but in this type of case, the stamens are said to be adjacent to the petals, producing an epipetalous flower.