Fig. 3

Wood formation of trees without (tree 3) and with (tree 2) intra-annual density fluctuation (IADF) formation. Cells have been double stained with red tones indicating mature xylem cells and blue tones indicating developing xylem cells and phloem cells. For the trees without IADF formation, the end of cell production (associated the end of cell enlargement phase) was observed on August 3 (DOY 216) (a), the lignification of xylem cells continues on August 16 (DOY 229) (b), and all the cells matured on September 2 (DOY 246) (c). For the trees with IADF formation, the first ending of cell production (associated the end of cell enlargement phase) was observed on August 3 (DOY 216) (d); however, wood production was followed again by earlywood-like cells and first observed on August 16 (DOY 229) (e), and the second end of cell production observed on September 2, DOY 246 (f). The white bar in each image represents 50 μm. CZ, cambial zone; EW, earlywood; LW, latewood; EWL, earlywood-like cells; LWL, latewood-like cells