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Abstract Detail

Development and Structure

L. Cunha Neto, Israel [1], Pace, Marcelo [2], angyalossy, Veronica [3].

When what seems successive cambia in Nyctaginaceae (Caryophyllales) is actually a new type of interxylary phloem.

For a long time, successive cambia have been the type of cambial variant most widely recognized for Nyctaginaceae. Despite the wide acceptance of this classification over time, other patterns of vascular anatomies were also proposed in the past by some researchers, which might indicate the occurrence of distinct ontogenies in the formation of the secondary stem body. However, the accurate identification of these developmental pathways has been undervalued due to the lack of ontogenetic research on a broader scale. In this study, we used the largest sampling ever carried to date (~60 species from 22 genera), to investigate the ontogeny of the stem in the main lineage in the family and document the real nature of the most common cambial variant present in Nyctaginaceae. Our analyses revealed that most species have an ontogeny that produces a type of interxylary phloem instead of successive cambia. Interxylary phloem is formed in species that start their vascular development with a polycyclic eustele (medullary bundles + continuous cylindrical procambium). Instead of forming multiple independent cambia, the cambial variant in the studied species developed through the activity of a single vascular cambium that produces secondary xylem and phloem at uneven rates around the circumference of the stem. Since this differentiated activity is established from the beginning of secondary growth, there is no formation of a regular cylinder of xylem and phloem in these species as observed in most eudicots. Besides, the irregular formation of the secondary xylem and phloem results in the presence of phloem strands immersed within a phloem parenchymatic matrix (sheathing axial parenchyma) which are enclosed in the secondary xylem. Unlike other groups with interxylary phloem, the arrangements of the phloem strands and sheathing axial parenchyma are extremely variable and produce different patterns: e.g., phloem islands, patches, or concentric bands. This study confirms for the first time the widespread occurrence of interxylary phloem in Nyctaginaceae and reveals the importance of comparative and developmental studies with a broad sampling of taxa. Our results also demonstrate the diversity of anatomical forms in Nyctaginaceae since successive cambia are still present in some lineages. Additional studies are being carried out and will provide an integrative approach to better comprehend the evolution of the development of the complex and diverse anatomies in Nyctaginaceae, that may still be hidden in groups that are theoretically widely explored, such as other Caryophyllales.

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1 - University Of Sao Paulo, Departamento De Botanica, Rua Do Matao, 277, Instituto De Biociencias, Cidade Universitaria, São Paulo, SP, 05508-090, Brazil
2 - Universidad Nacional Autónoma De México, Botánica, Circuito Zona Deportiva Sn De Ciudad Universitaria, Ciudad De Mexico, DIF, 04510, Mexico
3 - Universidade De São Paulo, Botany, Rua Do Matao 277, Sao Paulo, SP, 05508-090, Brazil

cambial variants
polycyclic eustele
secondary growth
stem anatomy.

Presentation Type: Oral Paper
Session: DS3, Development and Structure III
Location: /
Date: Thursday, July 22nd, 2021
Time: 1:00 PM(EDT)
Number: DS3012
Abstract ID:179
Candidate for Awards:Katherine Esau Award,Developmental and Structural Section Graduate Student Registration Award

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