The Making of Plant Armor: The Periderm

Abstract

The periderm acts as armor protecting the plant's inner tissues from biotic and abiotic stress. It forms during the radial thickening of plant organs such as stems and roots and replaces the function of primary protective tissues such as the epidermis and the endodermis. A wound periderm also forms to heal and protect injured tissues. The periderm comprises a meristematic tissue called the phellogen, or cork cambium, and its derivatives: the lignosuberized phellem and the phelloderm. Research on the periderm has mainly focused on the chemical composition of the phellem due to its relevance as a raw material for industrial processes. Today, there is increasing interest in the regulatory network underlying periderm development as a novel breeding trait to improve plant resilience and to sequester CO2. Here, we discuss our current understanding of periderm formation, focusing on aspects of periderm evolution, mechanisms of periderm ontogenesis, regulatory networks underlying phellogen initiation and cork differentiation, and future challenges of periderm research. Expected final online publication date for the Annual Review of Plant Biology, Volume 73 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The making of suberin

“…Cuticles are defined by the biopolymer cutin, a poly‐aliphatic polyester of fatty acids and fatty alcohols, with an additional presence of waxes, formed of unpolymerised alkanes, fatty alcohols and other compounds (Fich et al ., 2016). Older, radially thickened stems (including tubers) and roots, by contrast, form a multilayered protective tissue called the phellem (part of the periderm), or (outer) bark, that contains an even more complex arrangement of polymers in their walls (Serra et al ., 2022). Here, lignin‐like polymers are found in close association with an additional cutin‐like polymer, called suberin.…”

“…Suberin itself however, would have maintained the association with phenolic components and aromatic, lignin‐like polymers. The great physiological and ecological importance of suberisation has been covered by excellent reviews over previous years (Barberon, 2017; Campilho et al ., 2020; Harman‐Ware et al ., 2021; Holbein et al ., 2021; Shukla & Barberon, 2021; Serra et al ., 2022) and will not be the focus of this review. Instead, we will treat the many fundamental aspects of suberin formation that are still insufficiently understood: biosynthesis and transport, deposition and polymerisation, and native structure.…”

bHLH heterodimer complex variations shape meristems in Arabidopsis thaliana by affecting target gene specificity

“…While the apical meristems (RAM and SAM) give rise to the primary plant body, plants use the third pool of proliferating cells located in lateral meristems (LM) to support secondary growth leading to an increase in root and stem girth or thickness (Ragni and Greb, 2018). These meristems represent vascular and cork cambia (Etchells and Turner, 2010; Serra et al, 2022). Meristem activity is essential for growth and development and thus needs to be tightly controlled to ensure optimal growth depending on the environmental conditions and to avoid excessive cell proliferation (Motte et al, 2019).…”

Comparing anatomy, chemical composition, and water permeability of suberized organs in five plant species: wax makes the difference

“…However, the actual interface of roots directly facing the soil environment is formed by the rhizodermis and the hypodermis. The primary cell walls of these cell layers, especially the single or multi-layered hypodermis, are also characterized by the deposition of suberin (Hose et al 2001 ; Serra et al 2022 ). Tubers as storage organs of plants are characterized by a multi-layered periderm, which is suberized (Lulai and Corsini 1998 ).…”