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Almeida, Odair [1], Batista, Michelli [2], Rizzo, Beatriz [1], Beatriz, Santos [1], Sampaio, Paulo [3], Cardoso, Weverson [4], Souza, Luiz [2], Cota-Sanchez, Hugo [5].

Taxonomic significance of comparative floral anatomy in epiphytic cacti.

The cactus flower has sunken floral whorls in a vegetative shoot resulting in an external cover of receptacular tissue surrounding the ovary region, the pericarpel. In epiphytic cacti, the general floral attributes, such as variation in flower size, color, anthesis and nectar production (volume and sugar concentration), are known. However, floral anatomical structures are poorly investigated in epiphytic clades and the cactus family as a whole. The aim of this work was to compare several floral anatomical features among different epiphytic cacti. We analyzed three species (one Epiphyllum and two Selenicereus species from tribe Hylocereeae. Additional nine taxa from tribe Rhipsalideae were analyzed, from the genera Hatiora, Lepismium, Rhipsalis, and Schlumbergera. We used both light and scanning microscopy to inspect anatomical characters in search of morphological indicators separating taxonomic (tribal, generic and specific) levels. As expected, greater differences were found at the tribal level. In the Hylocereeae the apex of the tepal is glabrous. The columnar style is hollow in Selenicereus with internal epidermis with trichomes, and it is solid in Epiphyllum. The hypodermis in the pericarpel and floral tube has 2-3 layers of well-defined collenchyma cells, whereas the placenta region has a projection bearing several long and branched (Selenicereus) or unbranched funiculi (Epiphyllum), both with circinotropous ovules. Conversely, the Rhipsalideae has papillated tepal edges, one-to-two layers of hypodermis, solid columnar style, floral tube reduced, and ovules with short and unbranched funiculi. In addition, the Rhipsalideae exhibits some differences in ovule morphology. All the species have anatropous ovule, but in Schlumbergera and some Rhipsalis species there are intrusions of the ovary wall on the placenta region, which elevates the ovules in the locule. In close-related taxa, e.g., within subgenera of Rhipsalis and in the formas of Hatiora salicornioides the floral anatomy is not a good taxonomic indicator. The ramification of the funiculi and the filling of the style may indicate characters separating the Phyllocactoid and Hylocereoid clades, which share circinotropous ovules within Hylocereeae. Overall, this investigation shows that floral anatomy is significant to identify different lineages of epiphytic cacti, with better resolution at higher hierarchic taxonomic levels, mainly distinguished by perianth and gynoecium characters.

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Plant Morphology Lab

1 - São Paulo State University - UNESP, Praça Infante Dom Henrique, São Vicente, Sao Paulo, 11330900, Brazil
2 - Maringá State University, Maringá, Paraná, 87020-900, Brazil
3 - Santa Cecília University, Santos, São Paulo, 11045-907, Brazil
4 - Federal University of Rio de Janeiro , Museu Nacional, Rio de Janeiro, Rio de Janeiro, 20940-040, Brazil
5 - University Of Saskatchewan, Department Of Biology, 112 Science Place, Saskatoon, SK, S7N 5E2, Canada

floral morphology

Presentation Type: Oral Paper
Session: SYSTIV, Systematics IV: Eurosids & Basal Asterids
Location: Virtual/Virtual
Date: Wednesday, July 21st, 2021
Time: 4:00 PM(EDT)
Number: SYSTIV005
Abstract ID:507
Candidate for Awards:None

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