Question

Differentiate between the structure of the vascular bundle of a dicot stem and a monocot root.

Answer 1

Hint: Vascular bundle is composed of xylem and phloem present in all plant organs such as stems, leaves and roots. In stem vascular bundles are either scattered or located around the stem axis and in roots vascular bundles are radially arranged.

Complete step-by-step answer:
Vascular bundle is a strand of conducting tissues consisting of xylem and phloem. Vascular bundle originates from the primary stem. Xylem conducts water and dissolved minerals from root to the top of the plant. Phloem conducts food from site of synthesis to site of utilization.

S.No	Vascular bundle of dicot stem	Vascular bundle of monocot stem
1.	Almost all are of uniform size	Larger towards centre and smaller towards periphery.
2.	Arranged in a ring	Scattered
3.	Conjoint and open	Conjoint and closed
4.	Bundle sheath absent	Bundle sheath present
5.	Phloem parenchyma present	Phloem parenchyma absent
6.	Water-containing cavities are are absent	Water-containing cavities are present
7.	Vascular bundles are 2 to 6 in numbers	Vascular bundle are 6 in number

Vascular bundles in dicot stem:
Vascular bundles are arranged in a ring. Vascular bundles are 2 to 6 in numbers. In each vascular bundle xylem and phloem present together in one bundle (conjoint). The xylem and phloem located on the same radius with phloem towards the periphery (collateral) and in between xylem and phloem) cambium is present. Xylem is in endarch condition. In endarch, protoxylem is towards the centre and metaxylem towards the periphery. Example sunflower, beans stem.
Vascular bundles in dicot stem:
Vascular bundles in monocot roots are radially arranged. It consists of many patches of xylem and phloem. The number of vascular bundles are more than 6 (polyarch condition). Xylem is in exceptional condition. In exarch, protoxylem is periphery and metaxylem towards center. Examples: paddy, maize roots.

Note: In dicot stem vascular bundles are 2 to 6 numbers (diarch to polyarch), xylem is endarch condition and bundles are arranged in a ring. Whereas, in monocot root, vascular bundles are more than 6 numbers (polyarch), xylem is in exact condition and bundles are radially arranged.