Structural Characterization of Lignin in Four Cacti Wood: Implications of Lignification in the Growth Form and Succulence

Abstract

Wood lignin composition strongly depends on anatomical features and it has been used as a marker for characterizing major plant groups. Wood heterogeneity in Cactaceae is involved in evolutionary and adaptive processes within this group; moreover, it is highly correlated to the species growth form. Here we studied the lignin structure from different types of woods in four Cactaceae species with different stem morphologies (Pereskia lychnidiflora, tree/fibrous wood; Opuntia streptacantha and Pilosocereus chrysacanthus, tree/succulent fibrous wood; Ferocactus hamatacanthus, cylindrical stem/dimorphic wood) in order to determine their relationship with the wood anatomy in an evolutionary-adaptive context. Dioxane lignin was isolated and analyzed by pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS), two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The main linkages are the β-O−4′ ether (67–85%), the β-β′ resinol (10–26%) and the β-5′ and α-O−4′ linkages of the phenylcoumaran structures (≤7%). Spirodienone structures have a considerable abundance (5%) in the dimorphic wood of F. hamatacanthus. In addition, low contents (≤3%) of α,β-diaryl ether, α-oxidized β-O−4′ ether and dibenzodioxocin structures were found. The sinapyl- and coniferyl acetates are not part of the wood lignin in any of the studied species. The low (≤5%) γ-acetylation in the F. hamatacanthus and P. chrysacanthus wood lignin is here interpreted as an evidence of a high specialization of the wood elements in the conduction/storage of water. The lignin of the studied Cactaceae is composed predominantly of guaiacyl and syringyl units (S/G: 0.9–16.4). High abundance of syringyl units (62–94%) in three of the four species is considered as a defense mechanism against oxidative agents, it is a very conspicuous trait in the most succulent species with dimorphic wood. Furthermore, it is also associated with ferulates and the herein called γ-acetylated guaiacyl-syringaresinol complexes acting as nucleation sites for lignification and as cross-links between lignin and carbohydrates at the wide-band tracheid-fiber junctions.

Characterization of Phenolic Compounds Extracted from Cold Pressed Cactus (Opuntia ficus-indica L.) Seed Oil and the Effect of Roasting on Their Composition

“…Lignin is a phenolic biopolymer derived from hydroxy cinnamyl alcohols that differ in their degree of methoxylation: p -coumaryl, coniferyl, and sinapyl alcohols. It is formed under simple chemical control by bimolecular radical coupling reactions and its structure is highly dependent on the nature of monolignols and the cellular characteristics of the lignified tissue [ 49 ].…”

Differences in the Structural Chemical Composition of the Primary Xylem of Cactaceae: A Topochemical Perspective

“…The estimation of lignin composition has been made through different methods: pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS) (Klap et al, 2000), nuclear magnetic resonance (NMR) (Jin et al, 2007; Weng et al, 2010; Marques et al, 2016; Reyes-Rivera et al, 2018), Fourier transform infrared (FTIR) (Li et al, 2015; Reyes-Rivera et al, 2015; Reyes-Rivera et al, 2018), and high-performance liquid chromatography (HPLC) (Jaramillo-Carmona et al, 2008; Kline et al, 2010; Reyes-Rivera et al, 2015). For this reason, in this paper, Klason lignin is used directly to perform infrared (FTIR) spectrum readings, due to Reyes-Rivera et al (2018) finding consistent values when comparing these with other methods such as Py-GC/MS and NMR. Therefore, after the Klason lignin was obtained from the seedlings, the samples were kept in a desiccator and FTIR-ATR spectra were obtained using an Agilent Cary 630 FTIR-ATR equipment.…”

“…The chemical composition of secondary metabolites, analyzed by phytochemical profiling, has allowed the identification of the principal compounds in the stem (Loza-Cornejo et al, 2017), the structural chemical composition of stem conductive tissues (Reyes-Rivera et al, 2015; Maceda et al, 2018; Reyes-Rivera et al, 2018), and from other structures such as glochids and spines in several cacti species (Pritchard and Hall, 1976; Kohl et al, 2014).…”

“…The structural chemical composition of the secondary xylem of Cactaceae has been studied in fibrous, non-fibrous, and dimorphic species. The lignin concentration is the main component to distinguish fibrous species from non-fibrous ones (Maceda et al, 2018); also, the composition of lignin monomers is heterogeneous in non-fibrous and dimorphic species, but the occurrence of syringyl and guaiacyl is homogeneous in fibrous species (Reyes-Rivera et al, 2015; Reyes-Rivera et al, 2018). In addition, cellulose and lignin percentages differ with other families and between Cactaceae genera (Maceda et al, 2018).…”

Anatomy, Flow Cytometry, and X-Ray Tomography Reveal Tissue Organization and Ploidy Distribution in Long-Term In Vitro Cultures of Melocactus Species

“…Wide-band trachieds are a special type of tracheid with no perforations on their walls but instead possessing rigid secondary thickening bands ( Mauseth, 1999 ). A region of WBTs was reported in several species of cacti, including in Melocactus zehntneri and Melocactus bahiensis ( Mauseth et al, 1995 ; Mauseth and Plemons-Rodriguez, 1997 ; Mauseth, 1999 ; Stone-Palmquist and Mauseth, 2002 ; Arruda et al, 2004 ; Mauseth, 2004 ; Arruda et al, 2005 ; Mauseth, 2006 ; Melo-de-Pinna et al, 2006 ; Vázquez-Sánchez et al, 2007 ; Arruda and Melo-de-Pinna, 2010 ; Terrazas et al, 2016 ; Reyes-Rivera et al, 2018 ; Maceda et al, 2019 ). The paucity of support elements ( i.e.…”