Hello Hivers and Nature lovers, today I would like to write about a group of flowers that I think are impressive for their beauty and the complexity of their patterns. I am referring to a type of inflorescences that are commonly mistaken for simple flowers due to the high level of morphological and functional integration they present. These are the capitulum, among the best known of this type of inflorescences are daisies and sunflowers, although there is a great diversity of plants with this type of reproductive organ they are the typical reproductive structure of the plants of the Asteraceae family.
Flower or Inflorescence
Contrary to what some people believe, this type of reproductive structure is not a flower, but a group of flowers that grows close together in a modified branch that takes the name of receptacle. The flowers in the case of capitulum type inflorescences can have high functional specialization and consequently morphological modifications that facilitate their functions.
In the image above you can see a simple flower and a capitulum. If you look carefully you can see in the image on the left (which represents a simple flower) in the center has a set of structures in the form of head surrounded by the corolla of pink color, these are the male structures of the flower. However, in the image on the right towards the center what is observed is a set of small tubular structures surrounded by a set of ligule, each one of these tubules constitutes an independent flower.
Why capitulum?
According to the dictionary of botany, this term comes from the Latin word capitulum, which means capitate. Possibly referring to the shape of the receptacles or mature infructescences derived from some of these reproductive organs.
General structure
Although variety can be found in the structure of the flower heads, there are several general elements that are relatively constant in this type of inflorescence. The receptacle is the branch that carries the flower buds and supports the flowers. Only in this case it is modified into a compact structure usually in the shape of a head or cone.
Flowers, capitula typically have two types of flowers, tubular flowers and ray flowers, although some may have sterile flowers. A commonly found pattern is that the tubular flowers are arranged towards the center of the inflorescence and the ligulate flowers towards the outer edge. The ligule flowers are usually brightly colored. The set of ligule has a structure and function similar to that of the corolla of a single flower, to attract pollinators. On the other hand, there are inflorescences in capitulum that only have ligulate flowers.
Since the flower heads are composed of independent flowers, it is common for them to open at different times, generally starting from the edges towards the center of the inflorescence. And towards the end of the life of the inflorescence when all the flowers have opened it is often easier to see that it is indeed a set of independent flowers.
The flowers of the capitula generally produce achene-like fruits that can be naked as in the case of the sunflower or present ornamentations known as pappus.
These ornamentations are often related to dispersal mechanisms and can be in the form of hooks to attach to skin, hair or clothing.
Or they can be feathery increasing air resistance so that they act like sails and are associated with wind dispersion.
In any case, I consider that the chapters compose a set of inflorescences that are surprising for their beauty and complexity. As well as for the high level of specialization that they possess, and when they grow as a whole they can constitute quite a show.
All the images were taken by the author
The second image in the post was assembled in Canva
Translated with www.DeepL.com/Translator (free version)