Question

Polyarch conditions is found in
A. Monocot root
B. Dicot root
C. Monocot stem
D. Dicot stem

Answer 1

Hint:Vascular bundles are radial, closed with the exact condition of the xylem. There are a total eight bundles each of xylem and phloem tissues. The centre of these tissues is occupied by a central large pith which may be parenchymatous or sclerenchymatous.

Complete answer:
When there are more than four xylem arms, it is called a polyarch condition. Monocot plants usually have polyarch conditions.
A. In monocot root, vascular bundles are radial, closed with the exact condition of the xylem. There are a total eight bundles in each of xylem and phloem. When many strands of xylem are present, it is called polyarch condition, a characteristic feature of monocot root.
B. In dicot root, vascular bundles are in radial arrangement. Vascular bundles are described as radial and tetrarch. There are four bundles in each of xylem and phloem alternately. Xylem is described as exarch. So, it is not polyarch.
C. In monocot stems, the vascular bundles are scattered throughout the ground tissue. The vascular bundles are conjoint, collateral, endarch and closed. Xylem is described as endarch and it has only two protoxylem and two metaxylem vessels in each bundle. So, it is also not polyarch.
D. In the dicot stem, each vascular bundle is conjoint, collateral and open. Vascular bundles are eight in number and arranged in the form of a broken ring. Xylem is described as endarch. So, it is not polyarch.

Hence, the correct answer is option (A) i.e., Monocot root.
Note: Monocots are different from dicots in four structural features: leaves, stems, roots and flowers. But, the differences start from the very starting of the plant's life cycle: the seed. Within the seed lies a plant's embryo and monocots have one cotyledon (vein), dicots have two.