The primary structure of the root can be divided into three parts from the outside to the inside: epidermis, cortex and vascular column. The innermost layer of cells in the cortex is the inner cortex, the cells are arranged neatly and tightly, in the lateral wall and radial wall of the cell, often lignified and bolstered, in a ribbon around the cell, called casparian strip (casparian strip), in the transverse plane, the Casparian strip in the adjacent radial wall is a point, called Cayman point. The structure of the Cayman band on the inner cortex plays an important role in the exchange of water and solutes between the cortex and the tissue on both sides of the mesocolumn.

The Kjeller band staining kit mainly observed the Kjeler band in the vascular structure of plants in the initial root. Under ultraviolet excitation, the Kjeler band formed in the radial and transverse walls of the inner cortex showed yellow-white to yellow-green fluorescence, and the background was blue to blue-purple, with clear and sensitive coloring and stable performance.