Fig. 3

Light, polarized and fluorescence micrographs showing transverse views of cambium before the start of the experiment on 26 March 2015 (a–e). On this date, three to five layers of fusiform cambial cells were arranged compactly with no evidence of cell division, indicating inactive condition of cambium on the stem (a, b). A polarized light micrograph of thin sections after staining with safranin showing the cambial region (c). Expanding and expanded xylem cells were separated by observing the birefringence of cell wall. Fluorescence micrographs (d, e) showing the phloem, cambium and xylem. The heterogeneous intensity of fluorescence in (d, e) indicates the less-lignified xylem adjacent to cambium. Merged green (Ex/Em, BP450-490/BP500-550) and red (Ex/Em, BP539-563/BP570-640) image. Ap axial parenchyma, C cambium, Ph phloem, F fibers, Xy xylem. Bars = 50 µm