Tree Biology

Contents: - periderm - phellem - cork cambium - phelloderm - cortex - phloem- phloem rays - phloem - sieve tube element - companion cells - cambial zone (cambium) - bark - xylem - growth ring - vessels - tyloses - parenchyma - axial parenchyma - multiserrate ray parenchyma - uniserrate ray parenchyma - fibers - symplast - apoplast - growth ring/ray compartment - decay development

Click on any of the above terms to view its location in the tree cross section

Companion cells are alive and contain a nucleus. They are located adjacent to sieve tube elements which do not contain a nucleus. Companion cells help the sieve tubes function in moving sugars from leaves toward roots.