Fig. 3
![Fig. 3](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs10086-021-01950-2/MediaObjects/10086_2021_1950_Fig3_HTML.png)
Sample preparation process. a collection of micro-samples using a Trephor, b cutting a cross-section of the embedded micro-samples in PEG2000 (polyethylene glycol 2000) using a sliding microtome of thickness 6–12 μm, and c observation of thin sections under light (left) and polarized microscopes (right) to identify the cambial zone and xylem cells during enlarging, cell-wall thickening, and mature phases (scale bars, 100 μm)