Question

Identify the correct statements with reference to pericycle?
A. Distinguished in monocot stems.
B. Innermost layer of the cortex
C. Partly sclerenchymatous in roots
D. The seat of origin of lateral roots

Answer 1

The roots form an important organ system of the plants. Water and nutrients are absorbed by the root and enters the stem system and distributed to different parts of the plant by the xylem and phloem conducting tissues. The pericycle is present in the roots and sometimes in the stems of the plants. It encloses the vascular system.

Complete answer:

The outermost layer of the vascular tissues is called a pericycle. The pericycle is a single layered structure present interior to the endodermis and exterior to the vascular bundle. It consists of parenchymatous cells that are compactly arranged. In roots it is surrounded by an inner cortical layer known as the endodermis.

Pericycles in the dicot roots are made up of parenchyma tissues. Both in the young as well as matured stages in the dicot root pericycle is made up of parenchyma cells. In the monocots the pericycle is made up of parenchymatous tissues only in the young stage and it is replaced by sclerenchymatous tissues in the matured stage. In monocots, the pericycle is thus not distinguished.

The pericycle produces lateral roots which shows primary growth and during secondary growly vascular cambium is found. However, in the monocot roots during the primary growth lateral roots are produced by the pericycle.

The pericycles are related to various functions when present in various roots and shoots. In the roots the pericycles are responsible for lateral root formation and so they are the site of lateral root initiation process.

Hence, the correct answer is option (D).

Additional information:
The vascular tissues are xylem and phloem bundles which are arranged in a ring like structure. They are bounded by the pericycle layer which is the outermost layer of the stele. The main function of the pericycle is the support as well as protection of the plant. It supports the conducting tissues of the plants such as xylem and phloem. They do not provide any mechanical strength but protect the vascular bundle. The pericycle surrounds the vascular bundle and is not the innermost part of the cortex. In plants in which secondary growth takes place, the pericycle contributes to the formation of vascular cambium which finally forms the cork cambium.

Note: The pericycle is the lining of parenchyma or sclerenchyma cells that encircles the xylem and the phloem. The pericycle are unique cells as they are associated with root initiation particularly with the production of lateral roots. It gives rise to two types of meristem which are the vascular cambium and the cork cambium or the phellogen.