SR-FTIR Analysis of Rice Leaf Samples

The rice leaf samples were thinned to 7 μM before being scanned for SR-FTIR microspectroscopy. In all treatments, rice leaf samples were collected 7 days after the Xoo challenge. They were cut into 4 × 8 mM pieces and immediately coated with the Tissue-Trek optimum cutting temperature (OCT) compound (Electron Microscopy Sciences Inc., Hatfield, USA) and frozen. Until cryosectioning, each sample was kept at −80 °C. Through use of a Microm HM 525 Cryostat (Thermo Fisher Scientific), the sample was cut into small pieces with a thickness of 7 μM and the full leaf structure (epidermis and mesophyll) was preserved. The frozen rice leaves were placed on a BaF2 window, which is an infrared transparent material. To avoid the influence of water peaks in the examination, the water moisture in the sample was evaporated using a desiccator. The SR-FTIR spectra were chosen to be in the mid-infrared range [26 (link)].