PEDUNCLE: CHARACTERISTICS, STRUCTURE AND FUNCTIONS - BIOLOGY - 2024

The peduncle, in botany, is a floral structure that is responsible for supporting the flowers or inflorescences. It is herbaceous in texture, although in some species it becomes more woody.

The term "inflorescence" refers to a group or a set of flowers that are arranged together on a stem and born from a single branch - or from a complicated arrangement between the latter. Common examples of inflorescences are magnolias, tulips, and wheat.

Author: Pablo Alberto Salguero Quiles. commons.wikimedia.org

After being fertilized, the inflorescence becomes a fruit (in this case the correct term would be infructescence) and the peduncle continues to support it, basically becoming an extension of the stem. In case the fruit is very heavy, the peduncle is thicker and stronger to be able to support it.

Regarding its structure, the peduncle is basically a stem, with the typical vascular bundles. In certain cases, it may present additional elements such as bracts or trichomes, or it may be branched.

Botanists have classified flower stalks into almost ten categories, based on the shape of the flower and the way the flower is anchored to it.

It is also possible that the flower does not have this structure. In this case, they are called sitting flowers or sessile flowers. On the contrary, the term for flowers that do have a peduncle, is pedunculated.

characteristics

Flowers are the organs that are responsible for reproduction in the group of fanarogamous plants. It is a complex organ and is made up of a series of structures, among them a stem axis called the floral peduncle stands out.

The floral peduncle is characterized by being the prolongation that holds the inflorescences and widens in one of its terminal portions. This region is shared similar to a bud, but instead of producing true leaves, it is responsible for generating the four whorls that give rise to the flower.

This group of pieces (the sterile anthophiles: sepals and petals and the fertile ones: stamens and carpels) are also generally arranged concentrically.

The length of the peduncle can vary greatly depending on the species of plant studied. In certain flowers it can be very reduced, while in others it is totally absent.

In the absence of the peduncle, the term sessile or sitting is applied to express the lack of support. In botany, the term is also applied to the leaf when it lacks a stem, and to the anther when it lacks a filament.

Structure

The peduncle is similar to a stem

The peduncle exhibits a stem structure. In fact, it is a modified stem. Inside the peduncle, the conducting tubes of water, salts and nutrients run in the same way that occurs in the stems.

This set of tubes forms a wake in the thalamus, where each branch all its way to circulate towards the other pieces that make up the flower.

This structure widens at one end to give rise to the formation of the thalamus or receptacle (in some very specific species, such as roses, this structure is called hypanthus), which is surrounded by a set of apices that are responsible for forming the whorls of the flower.

Additional texture and structures

In the vast majority of flowers, the peduncle exhibits a rounded shape, although it can appear in any anatomically possible shape that a stem can acquire. Generally, it has a smooth or glabrous texture. However, some variants present trichomes or small villi.

Bracts can be found in its structure. The bracts are a type of modified leaves that are located in the proximity of the floral organ.

It is different from the average leaves of the plant and also from the perianth pieces - the non-reproductive portion of the flower formed by the corolla (set of petals) and the calyx (set of sepals).

Types of flower peduncles

According to the classification proposed by Jaramillo (2006), there are the following types of peduncles:

- Simple: they support a single flower, as in the case of the Gossypium genus.

- Bifloro: it supports a couple of flowers, as in the case of the Impatiens genus.

- Clusters: it supports multiple flowers and corresponds to the case found in inflorescences, as in the genus Trifolium. This type of peduncle is found in a large number of species.

- Axillary: the peduncle is located in the axillary region of the leaf or branch, as in the case of the Coffea genus.

- Head down: the structure is bent downwards, so that the flower remains as if it were hanging, as in the case of the genus Fuchsia.

- Caulinar: the peduncle originates from the trunk. This phenomenon is called cauliflora (in the flower) or caulicapia (in the fruit). Examples of this are the genera Theobroma, Annona and Crescentia.

- Petiolar: the peduncle originates from the petiole of the leaf by concrescence of the structures, as in the case of the genus Hibiscus.

- Terminal: the peduncle arises from the end of a stem or a branch. This phenomenon occurs in the Poaceae, Liliaceae, among other groups.

- Radical: the peduncle originates after the root, as in the case of the genus Gernium.

Features

The function of the flower stalk is to provide support and an anchoring site to a single flower, or to the group of flowers, the inflorescences. In the latter case, each individual flower is supported by a smaller stem, known as the pedicel. However, in some sources and books, the terms are used interchangeably.

However, it is not a structure present in all flowers, so its function is not totally essential. There are flowers that do not have the peduncle and still can carry out their life in a normal way.

As mentioned in the previous section, the widest portion of the peduncle is responsible for giving rise to all the organs of the flower, since it behaves like a bud.

References

1. Bentley, R. (1873). A Manual of Botany: Including the Structure, Functions, Classification, Properties and Uses of Plants. J. & A. Churchill.
2. Mauseth, JD, & Mauseth, JD (1988). Plant anatomy (No. 04; QK641, M3.). California: Benjamin / Cummings Publishing Company.
3. Peña, JRA (2011). Manual of plant histology. Editorial Paraninfo.
4. Plitt, JJ (2006). The flower and other derived organs. Caldas University.
5. Raven, PH, Evert, RF, & Curtis, H. (1981). Biology of plants.