Question

Periderm Includes
A. Cork cambium (phellogen), cork (phellem) and secondary cortex (phelloderm)
B. Cork cambium and cork
C. Cork
D. Cork and secondary phloem

Answer 1

The periderm is a cylindrical tissue that covers the surfaces of stems and roots of perennial plants throughout early secondary growth. It is not found in monocots and is confined to those gymnosperms and dicots that show secondary growth. Its main function is to ensure the protection of underlying tissues from desiccation, freezing, heat injury.

Complete answer:
Continued secondary growth if the vascular cylinder in many older roots and stems exert a pressure which results in the rupturing and stretching of the epidermis, cortex, and other tissue outside the secondary xylem. To avoid such breaking of external pressure, the plants develop a secondary protective covering. The secondary protective covering tissue consists of cork cambium, cork and secondary cortex, formed by a secondary lateral meristem called the Periderm.

Hence the right answer is Option A ( Cork Cambium, Cork and Secondary Cortex).

Additional Information: The Periderm is mostly found in roots and stem and dicots and gymnosperm. It doesn’t develop in the leaves and gymnosperm except for Yucca, Dracaena etc. The Periderm is always found in secondary growth. The periderm is also formed when a plant is wounded due to leaf or branch abscission, which is known as Wound Periderm. The formation of Periderm varies according to the plants, for example, Periderm is formed in Acacia plant at the beginning of the secondary growth and in the mango plant, it is formed after the plant is twenty years old.
A ring of cambium is made within the cortex of dicot stem, by the dedifferentiation of parenchyma is called Phellogen. This Periderm is involved in the formation of the periderm. The periderm consists of three different layers: phelloderm, phellogen and the phellem.

Note:
The main function of Periderm is to protect the underlying tissues from desiccation, freezing, heat injury, mechanical destruction, a different type of diseases, loss of epidermis, gaseous exchange through the lenticels and bounding tissues restricting the pathogens and insects. The periderm is a multilayered structure which replaces epidermis that undergoes secondary growth.