Promeristem is composed ofthree layers of cells in root tip,of them,outer layer of cells form the epidermis and root cap,centraland inner layers of cells sepratedly form the cortex and vascular cylinder.

• 其根端原分生组织具三层原始细胞，外层产生表皮和根冠，中层和内层分别产生皮层和中柱。