Ectopic cambia: Connections between natural and experimental vascular mutants

Abstract

One of the most remarkable innovations in the evolution of vascular plants is secondary growth: the developmental process by which plants grow thicker. The textbook illustration of secondary growth––a core of secondary xylem surrounded by a sheath of secondary phloem––is generated through a cylindrical meristem called the vascular cambium (Fig. 1A). This modality is conserved across thousands of species, providing mechanical support for ever‐elongating shoots, and a regenerative source of vascular tissues to feed the ever‐expanding crown of branches and leavesThis article is protected by copyright. All rights reserved.

The “abominable mystery” of Schenck: the polymorphism ofSerjania piscatoriaand its implications for the evolution of vascular variants in Paullinieae (Sapindaceae)

“…In the stem of S. piscatoria , these new cambia frequently generate circular units irregularly distributed along the circumference of the stem (in addition to eventual peripheral cylinders derived from the isolated vascular bundle). This pattern is a typical case of neoformations – new cambia forming independent, circular vascular units in an irregular fashion (Cunha Neto and Onyenedum, 2023) – similar to that described for stems (Tamaio and Angyalossy, 2009; Cunha Neto et al, 2018; Rizzieri et al, 2021) and roots (Bastos et al, 2016) of other Paullinieae species, and other families (e.g., Rubiaceae, Leal et al, 2020). In both S. piscatoria and other Paullinieae species, neoformations are produced after the establishment of other patterns of vascular variants, including successive cambia (Cunha Neto et al, 2018), which is also a type of ectopic cambia, as well as divided stems (Rizzieri et al, 2021), and compound stems (Tamaio and Angyalossy, 2009), which are cases of procambial variants (Cunha Neto 2023).…”