Mature Ranunculus root in cross section

Photographer

Clayton, Michael W.

Summary

• Photomicrograph
• Eudicot roots typically have a central vascular cylinder. The core is filled with xylem tissue that is fluted in outline. The ridges of this core of xylem are filled with protoxylem and are called protoxylem poles. In this example, there are four protoxylem poles, and is a tetrarch root. A root with three protoxylem poles is a triarch root. The number of protoxylem poles can vary in the same root in different sections.The valleys between the protoxylem poles are filled with strands of phloem. The innermost layer of ground tissue (of the cortex) forms the endodermis. The red-stained walls of the endodermis are inside of the primary wall and consist of alternating layers of suberin and wax. These walls are termed a suberin lamella. The suberin lamella is impervious to water. Note that some endodermals cells do not form a suberin lamella.