Fig. 4

Anatomic structures at different stages of SR development. a The anatomic structures of SR at different developmental stages. Safranin-Fast Green staining shows the cutinized cell walls in red and the cellulosic cell walls in green. The diameters of the AR, ISR, YSR and SR (S2.2) were 0.7 mm, 2.6 mm, 5.4 mm and 11.2 mm, respectively. Px, protoxylem; Co, cortex; Pp, primary phloem; Xpc, xylem parenchyma cell; Sx, secondary xylem; Msv, meristem surrounding vessels; Ca, cambium; Cpc, cortex parenchyma cell. b The images above show iodine-potassium iodide staining of starch granules in different stages of SR growth. Blue-black and brownish-black dots represent the starch granules. The images below show partially enlarged micrographs: the middle shows an image of the tissue near the cambium and meristem surrounding vessels in the SR, the left side shows an enlarged image of the meristem surrounding vessels in the centre, and the right side shows an enlarged image of the cambium. Black bars = 200 μm, red bars = 50 μm