primary xylem

…(apical meristems) give rise to primary xylem. In woody plants, secondary xylem constitutes the major part of a mature stem or root and is formed as the plant expands in girth and builds a ring of new xylem around the original primary xylem tissues. When this happens, the primary xylem…

…primary vascular tissue develops the primary xylem toward the inner aspect of the column and the primary phloem toward the outer aspect. The multiple vascular cylinders are arranged throughout the cortex, either in an uninterrupted ring between the cortex and pith or separated from each other by ground tissues. In…

Primary xylem (Figure 6) consists of lignified tracheary elements (tracheids and vessel elements), which are dead at maturity (they have lost their protoplasts). Parenchyma cells also are interspersed throughout the tissue. Both tracheids and vessel elements are long hollow cells with tapered end walls. The…

…most common arrangement of the primary xylem and phloem is called a collateral bundle; the outer portion of the procambium (adjacent to the cortex) becomes phloem, and the inner portion (adjacent to the pith) becomes xylem. In a bicollateral bundle, the phloem is both outside and inside the xylem, as…