Issue 29, 2023

Variable lignin structure revealed in Populus leaves

Abstract

Lignin has long been a trait of interest, especially in bioenergy feedstocks such as Populus. While the stem lignin of Populus is well studied, foliar lignin has received significantly less consideration. To this end, leaves from 11 field grown, natural variant Populus trichocarpa genotypes were investigated by NMR, FTIR, and GC-MS. Five of these genotypes were sufficiently irrigated, and the other six genotypes were irrigated at a reduced rate (59% of the potential evapotranspiration for the site) to induce drought treatment. Analysis by HSQC NMR revealed highly variable lignin structure among the samples, especially for the syringyl/guaiacyl (S/G) ratio, which ranged from 0.52–11.9. Appreciable levels of a condensed syringyl lignin structure were observed in most samples. The same genotype subjected to different treatments exhibited similar levels of condensed syringyl lignin, suggesting this was not a response to stress. A cross peak of δC/δH 74.6/5.03, consistent with the erythro form of the β-O-4 linkage, was observed in genotypes where significant syringyl units were present. Principle component analysis revealed that FTIR absorbances associated with syringyl units (830 cm−1, 1317 cm−1) greatly contributed to variability between samples. Additionally, the ratio of 830/1230 cm−1 peak intensities were reasonably correlated (p-value < 0.05) with the S/G ratio determined by NMR. Analysis by GC-MS revealed significant variability of secondary metabolites such as tremuloidin, trichocarpin, and salicortin. Additionally, salicin derivatives were found to be well correlated with NMR results, which has been previously hypothesized. These results highlight previously unexplored nuance and variability associated with foliage tissue of poplar.

Graphical abstract: Variable lignin structure revealed in Populus leaves

Supplementary files

Article information

Article type
Paper
Submitted
11 mei 2023
Accepted
25 jun 2023
First published
05 jul 2023
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2023,13, 20187-20197

Variable lignin structure revealed in Populus leaves

N. Bryant, N. Engle, T. Tschaplinski, Y. Pu and A. J. Ragauskas, RSC Adv., 2023, 13, 20187 DOI: 10.1039/D3RA03142J

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