The Flowering Unit in the Synflorescences of Amaranthaceae

Abstract

The structure of the synflorescence and the flowering units in Amaranthaceae are characterized. The synflorescence is polytelic. In the flowering unit we recognize the main florescence and the enrichment zone. The florescences may consist of: (1) Fully developed partial florescences bearing three or more flowers; (2) Partial florescences reduced to one or a few fertile flowers having prophylls with more or less modified axillary productions; or (3) No partial florescences but solitary flowers having prophylls with no axillary productions. We described the flowering unit in species with florescences bearing a solitary flower and the flowering unit in species with florescences bearing partial florescences. Hypothesized developmental processes are described, with a view to finding relationships among different models characterized in the family as well as defining characters for cladistic studies, which may be useful to depict all the variations observed.

Disentangling confusions in inflorescence morphology: Patterns and diversity of reproductive shoot ramification in angiosperms

“…A number of families were treated in Troll & Weberling (1989) and Weberling & Troll (1998). Studies on an order or single families have also been performed, such as in Myrtales (Weberling, 1988b), Amaranthaceae (Urmi‐König, 1981; Acosta et al, 2009), Hamamelidaceae (Endress, 1970), Fabaceae (Weberling, 1989b), Bruniaceae (Classen‐Bockhoff, 2000), Poaceae (Vegetti & Anton, 1995), Cyperaceae (Vrijdaghs et al, 2010), or Eriocaulaceae (Stützel, 1984). From these studies it can be seen that, for example, Papaveraceae, Berberidaceae, and Ranunculaceae are largely characterized by thyrsoids and panicles (Weberling & Troll, 1998), Hamamelidaceae by racemes or spikes (without terminal flowers) and panicles in some nested genera (Endress, 1970), Betulaceae by thyrses (Abbe, 1974), and Poaceae and Cyperaceae by compound inflorescences with spikes as units (see below; Vegetti & Anton, 1995; Vrijdaghs et al, 2010).…”

Enigmatic floral structures in Alternanthera, Iresine, and Tidestromia (Gomphrenoideae, Amaranthaceae). A developmental homology assessment

“…2I) consists of about 100 species mainly in the New World. It is characterised by an invariable floral structure, which contrasts with the a large variation in The inflorescences of Amaranthaceae sensu stricto are terminal or axillary, spiciform or capitate, sometimes compound racemes or panicles (see for example Eliasson 1988, Townsend 1993and Acosta et al 2009). Eliasson (1988) mentioned clusters of flowers that he called 'cymules' consisting of a terminal flower and lateral flowers in its bracteoles.…”

Gomphrena (Amaranthaceae, Gomphrenoideae) diversified as a C4 lineage in the New World tropics with specializations in floral and inflorescence morphology, and an escape to Australia

“…The head-like shape was maintained in the Gomphrena clade whereas elongate to cylindric paracladia with remote flowers were independently derived in Hebanthe and Froelichia (not illustrated). The arrangement of paracladia into more complex synflorescences (character 8; partial florescences) is variable in Gomphrenoideae (Acosta & al. 2009) and also considerably differs in Gomphrena and allies depending on the branching system of more or less complex synflorescences.…”

“…Cauline leaves supporting branches in synflorescence. Character 10 The paracladia may appear in a complex branching system (synflorescence) where the respective cauline leaf organs are not just reduced in size but considerably modified and differ from the other normal photosynthetic cauline leaves also in texture and anatomy (Acosta & al. 2009).…”

“…(2019) studied the ontogeny of Blutaparon, Guilleminea and several species of Gomphrena and Pfaffia which have lateral appendages on both sides of the filament but no alternating stamen tube appendages, and concluded that these lateral appendages are de novo organs not homologous to the stamen tube appendages. Acosta & al. (2009) compared the structure of synflorescences across Amaranthaceae, and found that Gomphrenoideae possess thyrsoid structures with paracladia reduced to solitary flowers but they did not examine Gomphrena in more detail.…”