What is meant by Pericycle?

Pericycle cells are plant tissues that provide support and store nutrients. They are made up of two types of cells: parenchyma and sclerenchyma. In some plants like cucurbits, pericycle cells are mostly sclerenchyma, while in plants like sunflower, they have both parenchyma and sclerenchyma.

Parenchyma cells in the pericycle are non-vascular (do not transport water over long distances). Their main job is to store nutrients and move them over short distances. Sclerenchyma cells, on the other hand, also do not transport water or nutrients but give strength and protection to the plant.

In dicot stems, pericycle cells form a multilayered zone between the endodermis (outer layer) and the vascular bundles (xylem and phloem). The inner boundary of this zone is the primary phloem, while the outer boundary is the endodermis. Pericycle cells are considered part of the vascular system because they surround the xylem (transports water) and phloem (transports nutrients).

In roots, pericycle cells are similar to those in stems. They also help form new roots, support the plant structure, and protect the roots. Root pericycle cells are mostly thin-walled parenchyma, and they play a key role in forming lateral roots, which allow the plant to grow bigger and stronger.

Note:

• In most roots, the pericycle is a single layer of cells (uniseriate), but in some plants like smilax, it is multilayered and sclerenchymatous.
• Most roots have a clear pericycle, but some parasitic or aquatic plants do not.

Functions of Pericycle Cells:

1. Can become meristematic (able to divide) to form vascular cambium and phellogen in dicot roots.
2. Give rise to lateral roots and adventitious roots from stems.
3. Some pericycle cells also function in storing nutrients.