Observation-guide
Morphology of the floral receptacle in Asteraceae: a guide to observing heads
Observation guide on the structure of the receptacle and the organization of flowers in Asteraceae heads, based on descriptive botanical terminology.
The receptacle as the floral axis
In the angiosperm flower, floral parts are arranged around a specialized stem whose insertion region is called the receptacle, floral axis, or thalamus. This axis can exhibit various morphologies: it can be a continuation of the stem, expand in the shape of a plate or head, or become a concavity, as occurs in flowers with an inferior ovary. The shape of the receptacle, along with the position and number of the floral parts inserted in it, constitutes a fundamental trait in taxonomic descriptions and in the construction of identification keys, as they are quick and economical data to record that require little or no special technique. [7575]
The head as a pseudanthium
In the context of the family Asteraceae, the head is defined as a specific form of the receptacle that presents an involucre below. Botanically, this structure is classified as a pseudanthium, a term that designates a unit that appears as a single flower but typically consists of two or more flowers that function as a single floral syndrome. Pseudanthia can be presented as heads, as in the case of Asteraceae, or as spadices, as in Araceae. This organization allows multiple individual flowers to operate in an integrated manner, differentiating them from true flowers or euanthia. [7575]
Arrangement of floral parts
The arrangement of floral parts on the receptacle varies according to the family considered. In spiral arrangement, the parts are inserted consecutively and at different levels, describing a spiral on the axis. In whorled or cyclic arrangement, the parts are inserted at several nodes of the axis, arranging themselves in whorls or cycles, where each floral part of a whorl alternates with the parts of the next. The order in which the parts are arranged on the floral axis never varies, although some part may be missing, and the axis never ceases to be determinate, that is, it exhausts its growth after producing the last floral part. [7574, 7575]
Observable traits in the perianth
In the observation of Asteraceae, the reduction of the perianth parts is notable. The sepals, which form the calyx, can be reduced to structures such as teeth or bristles that constitute the pappus. This modification is a distinctive trait of the family and differs from other families where the calyx can be ephemeral, deciduous, or persistent. The corolla, formed by the petals, is the inner whorl of the perianth that surrounds the fertile parts and generally presents parts larger and more colored than those of the calyx. [7577, 7575]
Sources and method
This story synthesises the references below and separates possible observations from conclusions that would need more evidence. It does not present original FaunaGuide fieldwork or replace expert identification.
- Morfología floral — Partes de la flor Partes de la flor Partes de una flor madura. Pulsa en los nombres para navegar. (Ver imagen) En botánica, se llama morfología floral al estudio de la diversidad de formas y estructuras que presenta la flor que, por definición, es una ram
- Terminología descriptiva de las plantas — In this article se detectaron varios problemas. Por favor, edítalo y/o discute los problemas en la discusión para mejorarlo: Las referencias no son claras o tienen un formato incorrecto. Podría ser demasiado largo, y algunos navegadores podrían tener dif
- Морфологија цвета — Чашични листићи могу имати различиту конзистенцију и облик. Код главочика (Asteraceae), на пример, чашични листићи су редуковани у длачице или чекиње које чине папус (паповку). У зависности од свог трајања у односу на остале цветне делове, чашица може бит