Abstract:To have a better understanding of the special texture structure of stem transverse section of Haloxylon ammodendron, based on the CT scan image, the three-dimensional image of the growth ring was reconstructed by extracting the outside envelope of the rapid growth band, and formative cause of the two-dimensional texture characteristics was revealed from the three-dimensional texture characteristics. It is found that there was a direct connection between the rapid growth band of Haloxylon ammodendron, that was, there was the transverse conjunction between the vessels of each growth ring layer. In this study, the spanning structure between adjacent growth ring vessels was named as the connecting bridge structure, which is an efficient channel for the transverse transport of water. The secondary xylem of Haloxylon ammodendron lacks wood rays, and its water transverse transport function was completed by a transverse transport system composed of the connecting bridge structure. The connecting bridge structure was also responsible for the intermittent spiral of the cross-sectional texture in secondary xylem of Haloxylon ammodendron. The connecting bridge structure was divided into two basic interlayer spanning modes: transverse one and longitudinal one. The average value of the approximately elliptical discontinuous opening caused by the transverse connecting bridge in the rapid growth ring was 0.51 mm2, and the average value of the discontinuous opening caused by the longitudinal connecting bridge was 0.17 mm2. On average, 6—7 connecting bridge structures were connected in series to form a bridge group and distributed radially in the secondary xylem of Haloxylon ammodendron, most of the bridge group were inclined upwards, while a few were inclined downwards, and the tilt angle was between ±13.2—17.46°. The bridge group formed by the connecting bridges in series realizes fast transverse transport of water in secondary xylem of Haloxylon ammodendron, played the function of wood rays in the secondary xylem of other plants, and formed a unique water transportation system adapted to the arid environment. Using the reconstructed 3D texture image of the growth ring, the observer can clearly distinguish between the bridging structure and the growth ring layer through longitudinal observation. The results of this study have far-reaching implications. Firstly, it was conducive to the counting of growth rings. Secondly, it was beneficial to investigate the age structure of the population of Haloxylon ammodendron. Thirdly, it also provided new research interests for revealing the growth law of Haloxylon ammodendron at the physiological, ecological and molecular levels.