Analytical Sciences

IR-SNOM Analysis of Occluding Substances in Lumina of Xylem Elements in Sapwood of Quercus serrata Attacked by Platypus quercivorus

Takayuki YAMAGISHI,* Kento AIZAWA,** Toshihiro YAMADA,*** and Yuji MATSUMOTO*

*Laboratory of Wood Chemistry, Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan
**IR & Raman Engineering Division, Jasco Co., Ltd., 2967-5 Ishikawa, Hachioji, Tokyo 192-8537, Japan
***The University of Tokyo Chiba Forest, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 770 Amatsu, Kamogawa, Chiba 299-5503, Japan

A new microspectroscopic technique was applied to the analysis of occluding deposits in xylem elements of Quercus serrata. The production of this substance is believed to be a defense response of the sapwood against fungal infection. An occluding substance about 10 μm across was analyzed by Infrared-Scanning Near-field Optical Microscopy (IR-SNOM), which allows for the measurement of IR spectrum with high spatial resolution. The near-field IR spectrum of an occluding substance was different from those of xylem elements and featured a lack of the clear C–H absorption band that should appear at 3000 – 2850 cm⁻¹. On the other hand, the absorption band of ester bond exhibited a very strong peak. Among the near-field IR spectra of related compounds, a similar ester absorption peak was observed in the spectrum of pectin and tannic acid. The presence of a C–H absorption band as a very week peak was similar to (+)-catechin and tannic acid.

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