Fig. 1

Conventional light and confocal laser scanning microscopic (CLSM) images showing the bark structure just before the formation of new periderm (Stage 0) in Tree A in June, 2016. Light micrographs of a transverse section (a, e) and a radial section (b, f) without staining showing the cell morphology and arrangement. c, d, g, h CLSM images of the same sections of a, b, e, f after stained with fluorol yellow 088 (FY) and Congo red (CR). e–h Higher magnification images of the selected areas in a–d. White arrows indicate the innermost periderms. AP axial parenchyma cell, F phloem fiber, IB inner bark, OB outer bark, Pd phelloderm, Pg phellogen, Ph phellem, Pr periderm, Rh rhytidome, RP ray parenchyma cell, S sieve cell. The right side of each micrograph corresponds to the outer side of the tree. Scale bars = 200 µm in a–d; 50 µm in e–h