many textbooks have not been updated. Although the cell wall of the endothelium is rich in woodbolic??(what does "woodbolic" even mean?suggest a better term), this is the result of the sublevel differentiation of the endothelium . In the past, some scholars believe that the formation of the Endodermis of Casparian strip is the beginning of sublevel differentiation, but there is no direct relationship between the two. The casparian strip has formed after the primary differentiation of the , and the secondary differentiation begins with the slash cut of the root, not where the Casparian strip is. Function The casparian strip is fully filled with the gap between endothelial cells, including the middle lamella, making the cell walls of the two cells almost fused. In the transportation of water and inorganic nutrients at the root of plants, the Casparian strip mainly affects the transportation of primary in vitro, that is, the transportation of water and inorganic salts through the interstitial cells of the epidermis and cortex cells. When water and inorganic salt come to the endothelial cells, they need to enter the cell through the cell membrane because the casparian strip is not water-permeable, and then transported by the protoplasmic inner path to reach the lignan cells of the stele, and then to other organs such as the stems and leaves. When the growth environment is unfavourable, the casparian strip can act as a barrier between plant cells and the outside world, avoiding the entry of ions or outflow of their own ions in the environment. In addition, the thickening of the carcass belt and the cortex also prevents toxic substances or pathogen invasion, as well as the function of preventing water dispersion. Some studies have shown that plants may form thicker casparian strip in high-salt environments, and in areas closer to the tip of the roots, which may be an adaptation to the environment, but compared with the endothelial sublevel differentiated wooden bolt walls, which are significantly thickened in high-salt adversity, the casparian strip changes is smaller. The casparian strip is mainly located in the exodermis of the root, but some plants also have the casparian strip in the outer cortex on the outer side of the root cortex, stem or leaf. For example, the conifers of Pinus bungeana and the stems of Pelargonium have the casparian strip, which may be related to preventing water dispersion or pathogenic invasion. Development