Rapid phytochemical analysis of birch (Betula) and poplar (Populus) foliage by near-infrared reflectance spectroscopy

Abstract

Poplar (Populus) and birch (Betula) species are widely distributed throughout the northern hemisphere, where they are foundation species in forest ecosystems and serve as important sources of pulpwood. The ecology of these species is strongly linked to their foliar chemistry, creating demand for a rapid, inexpensive method to analyze phytochemistry. Our study demonstrates the feasibility of using near-infrared reflectance spectroscopy (NIRS) as an inexpensive, high-throughput tool for determining primary (e.g., nitrogen, sugars, starch) and secondary (e.g., tannins, phenolic glycosides) foliar chemistry of Populus and Betula species, and identifies conditions necessary for obtaining reliable quantitative data. We developed calibrations with high predictive power (residual predictive deviations ≤ 7.4) by relating phytochemical concentrations determined with classical analytical methods (e.g., spectrophotometric assays, liquid chromatography) to NIR spectra, using modified partial least squares regression. We determine that NIRS, although less sensitive and precise than classical methods for some compounds, provides useful predictions in a much faster, less expensive manner than do classical methods.

Spectroscopic determination of ecologically relevant plant secondary metabolites

“…Specifically, the combination of individual compounds increases the probability that a detection threshold of concentration, and its subsequent effect on leaf spectra, will be surpassed (Rubert‐Nason et al . ). We found that the prediction of tremulacin in fresh leaves across 500 permutations of the data was more stable than that of salicortin.…”

“…; Rubert‐Nason et al . ; Kokaly & Skidmore ). Moreover, coefficient weightings and VIP statistics from models predicting tannins and salicinoids were most pronounced in these literature‐reported regions, corroborating the conclusion that the bending and stretching of C–H and O–H bonds are important for spectroscopic prediction of plant phenolics (Shenk, Workman & Westerhaus ; Kokaly & Skidmore ).…”

“…; Kokaly & Skidmore ), (ii) our previous work showed strong relationships at these wavelengths for predictive models of phenolic compounds using dried foliage of the same tree species (Rubert‐Nason et al . ), and (iii) it avoids leveraging correlations between phenolics and pigments in the visible wavelengths.…”

“…; Couture, Serbin & Townsend ; Rubert‐Nason et al . ). Of the major groups of secondary metabolites, phenolic compounds are a group of secondary metabolites universally distributed in the plant kingdom and play influential roles in plant physiology and ecosystem functioning.…”

Functional characterization of CCR in birch (Betula platyphylla × Betula pendula) through overexpression and suppression analysis

“…This species has high cold‐tolerance (Li et al , Puhakainen et al ) and is widely planted in north China. It is an economically important tree species and its wood is used primarily for lumber, pulpwood, fuelwood and plywood (Valanne , Lannenpaa et al , Pavlo et al , Reimann et al , Borrega et al , Huang et al , Rubert‐Nason et al ). It is worth emphasizing that birch wood is particularly suitable for making plywood.…”