Question

Vascular bundle with protoxylem towards the periphery is
A. Radial
B. Endarch
C. Exarch
D. Closed

Answer 1

Hint: The vascular tissue system is a complex tissue system consisting of phloem and xylem. The vascular bundle is formed with the presence of both xylem and phloem. The vascular bundles are of different types based upon the presence of cambium, and location of xylem and phloem.

Complete answer:
In roots and stems, the arrangement of xylem and phloem are different. In roots, the xylem and phloem are arranged in an alternate manner (on different radii) in a vascular bundle. This arrangement is known as a radial arrangement. In stems and leaves, the xylem and phloem are present in the same radius. This arrangement is known as conjoint.
The primary xylem has two types – protoxylem and metaxylem. Protoxylem is the first formed xylem element and metaxylem is formed later. The arrangement of protoxylem and metaxylem are also different in roots and stems. In the stems, the protoxylem is present towards the center (pith) and the metaxylem towards the periphery. This arrangement is known as Endarch. While in roots the protoxylem is present towards the periphery and the metaxylem is present towards the center. This arrangement is known as Exarch.

Hence, the correct answer is option (C).

Note: In dicotyledonous and monocotyledonous plants, the arrangement of the vascular bundle is different. In dicots, cambium is present between the xylem and phloem. The cambium has the ability to form secondary xylem and phloem tissues. This is known as the open vascular system.
In a closed vascular system, there is no cambium between the xylem and phloem. This type of arrangement is seen in monocots and secondary tissues are not produced in them.