Anatomy Of Flowering Plants

Vascular bundles are classified based on their arrangement and nature:

• Conjoint Vascular Bundles: Xylem and phloem are arranged together on the same radius.
• Open Vascular Bundles: Cambium is present between xylem and phloem, which allows secondary growth.
• In the dicot stem, the vascular bundles are conjoint, collateral, and open, facilitating secondary growth.
• In contrast, monocot stems and roots usually have closed vascular bundles (without cambium), and roots of both monocots and dicots show radial arrangement, not conjoint bundles.

Thus, conjoint, open vascular bundles are characteristic of the dicot stem.