Mplan 100 oil immersion microscope objective

The raw and pretreated wood sections were placed on a glass slide with a drop of D₂O and then covered with a glass coverslip of 0.17 mm thickness for Raman detection. A LabRam Xplora exquisite full-automatic confocal Raman microscope (Horiba Jobin Yvon, Longjumeau, France) equipped with an MPlan 100× oil immersion microscope objective (Olympus, NA = 1.40) was utilized in this study. A linear polarized laser (diode-pumped green laser, λ = 532 nm), focused with a diffraction-limited spot size (0.61 λ/NA), was used to conduct measurements. The laser power on the sample was approximately 8 mW. The Raman light was detected by an air-cooled, front-illuminated, spectroscopic charge-coupled device (CCD) behind a grating (1200 grooves·mm⁻¹) spectrometer. For mapping, an integration time of 2 s was chosen and every pixel corresponds to one scan with a spectrum acquired every 0.5 µm by averaging 2 s cycles. Labspec 5 software (Horiba Jobin Yvon, Longjumeau, France) was used for spectra analysis and image processing.

The samples for Raman analysis were taken from the air-dried stems. Serial of 16-μm-thick cross-sections were cut using a sliding microtome (Leica SM 2010R, Wetzlar, Germany) from the three parts of CK and transgenic poplars for Raman analysis. A LabRam Xplora exquisite full-automatic confocal Raman microscope (Horiba Jobin Yvon, Paris, France) equipped with an MPlan 100× oil immersion microscope objective (Olympus, NA = 1.40) was utilized. A linear polarized laser (diode-pumped green laser, λ = 532 nm), focused with a diffraction-limited spot size (0.61λ/NA), was used to conduct measurements. The laser power on the sample was approximately 8 mW. For mapping, an integration time of 2 s was chosen and every pixel corresponds to one scan with a spectrum acquired every 0.4 μm by averaging 2 s cycles. The Spectrum 6 software package was used for spectra analysis and image processing.