Answer:
As the plant grows, existing bundles grow larger and thicker providing structural support.
Step-by-step explanation:
In the dicot stem, rather than being scattered throughout the plant interior, the vascular bundles are arranged in a ring, with pith concentrated at the core of the stem.
In each vascular bundle, the xylem and phloem are separated by a substance called vascular cambium.
As the plant grows, existing bundles grow larger (rather than new vascular bundles being generated, as in monocots). The vascular cambium operates by producing new xylem and phloem cells, which in turn pushes the old cells outward and forces the bundle to grow.
Note: Development in woody dicots, includes a lateral system of nutrient transport in which vessels called rays extend horizontally from the phloem to the pith, carrying nutrients to the pith for storage or to the phloem for dispersal.