ROOTS
Primary Growth
The rootcap is derived from the root apical meristem. It consists of parenchyma cells and serves to protect the root tip as it grows through the soil. As new rootcap cells are formed, the older cells are pushed off.
The root apical meristem is not visible in the image at left, but is located superior to the rootcap. The root apical meristem gives rise to initial cells, which, in turn, divide and differentiate into cells that make up the rootcap, epidermis, cortex, endodermis, and vascular tissues.
The image at left illustrates the positions of the three primary tissue systems in the root.
Primary Root LS
In the image at left, the endodermis appears to have become lignified. The protoxylem and metaxylem make up one primary xylem arch. Primary phloem is located between these arches. This root demonstrates a hexarch pattern of six xylem archs.
