Fig. 5

SEM micrograph of the radial and bottom views of sample A. a An image was taken from the radial view at the white circle in Fig. 3a. The right side of the image shows the transverse surface of the tracheids, and the left side of the image displays the longitudinal surface of the tracheids. A white arrow indicates the direction of gravity. Scale bar, 100 µm. b An image taken from the bottom-view at the white circle in Fig. 3a. The left side of the image shows the tracheids curving in a horizontal plane. The direction of gravity is from the reverse side to the front side. Scale bar, 100 µm. c The schematic illustration of the observation angles to sample A for (a) and (b) images. d An enlarged image of the zone outlined by the white rectangular area in (b) suggests that tracheids have bordered pits. Scale bar, 50 µm