Question

Cork cambium of dicot stem originates from?
A. Dedifferentiated parenchyma cells of the cortex
B. Dedifferentiated collenchyma cells of the cortex
C. Parenchyma cells of medullary rays
D. Parenchyma cells of pericycle

Answer 1

Hint: Cork cambium refers to a lateral meristem. It forms as a result of secondary growth mainly in the woody trees. It works as a protective layer formed in the plant.
It is formed as a secondary meristem from a layer of collenchyma or parenchyma immediately beneath the epidermis.

Complete answer:
Option A- Dedifferentiated parenchyma cells of the cortex
Dedifferentiation is the phenomenon in which the living differentiated cells that have lost the capacity to divide, regain their capacity of the division under certain conditions. For example, interfascicular cambium and cork cambium, or the fully differentiated parenchyma cells from meristems.

Option B- Dedifferentiated collenchyma cells of the cortex
Secondary growth occurring in the cortex of the dicot stem is known as extra stelar secondary growth. It occurs by forming a ring of meristematic tissue known as cork cambium or phellogen by the dedifferentiation of collenchyma present in the cortex. It undergoes periclinal divisions and produces cells towards the outer side and inner side. The cells towards the outer side change into cork or phellem and the cells towards the inner side change into the secondary cortex or phelloderm. Cork, Cork cambium, and secondary cortex together are known as Periderm.

Option C- Parenchyma cells of medullary rays
The cells that are cut out by the cambium towards the periphery are phloem parenchyma while those towards the pith are xylem parenchyma. Both of these cells work together as secondary medullary rays. These medullary or pith rays are crucial for the radial conduction of the water, minerals, and other organic substances.

Option D- Parenchyma cells of pericycle
The pericycle is a cylinder of parenchyma or sclerenchyma cells. It lies just inside the endodermis. It is the outermost part of the stele of plants. The plants that undergo secondary growth, the pericycle contributes to the vascular cambium that often diverges into a cork cambium.

So, the correct option is B- ‘Dedifferentiated collenchyma cells of cortex’.

Note: The cork cambium produces bark. In dicot stems, the vascular cambium originally differentiates from procambial cells within the vascular bundles. This fascicular cambium contributes additional cells to both the xylem and the phloem of the bundle.