Mature Beta stem

 

In the mature beetroot stem, primary vascular bundles become irregularly distributed  and these arise as a succession of arcs or rings of vascular cambium.  One such bundle is shown in the micrograph to the right. This large vascular bundle is entire, and is associated with phloem, (P) which is separated from the secondary xylem (2X) by a cambial zone (CZ). Internal to this, is a zone of well-developed xylem containing clustered metaxylem vessels (MX). Protoxylem (PX) occurs on the inner face of this bundle.