Fig. 1

Width/thickness ratio and anatomical structures of leaf cross sections of the representative Pinaceae species. a Dot boxplots with an example of the width and thickness measurement shown at the top left. Red boxes, species with needlelike leaves; blue boxes, species with flattened leaves. The two boundaries of the box correspond to the 25 and 75% percentiles, respectively. The internal horizontal line and square indicate the median and mean values, respectively. b SEM micrographs of leaf anatomical structures of the species as shown in (a) with the same number, except number 9, which represents Tsuga forrestii. Green color, palisade tissue; red arrow, the direction of cell arrangement. Bars, 100 μm. c SEM micrographs of leaf vasculatures of the species as shown in (a) with the same number. Purple color, xylem; blue color, phloem. Bars, 100 μm