, What is periderm? How does periderm formation take place in the dicot stems?
Periderm is a group of cells that substitute for the epidermis in the plant. The periderm may be found in fruits, but its primary role is to provide protection to the roots and the stem. The periderm is observed in gymnosperms and dicotyledons. They are absent in leaves and monocots. The periderm is formed by three main types of tissues: Phellogen (cork cambium).Phelloderm (secondary cortex).Phellum (cork). For the stem to increase its girth, the epidermis and the cortex are replaced by a different type of meristematic tissue called the cork cambium, or the phellogen. The phellogen is mersitematic and divides into cells both on the outside as well as on the inside. The cells towards the inner side develop into phelloderm, or secondary cortex. In some plant species, the phelloderm is completely absent. The phelloderm contains chloroplasts, which help in photosynthesis and cellulose fibres. The cells on the outer side form the phellum, or the cork. The cells of this layer are characterized by suberin deposits, thereby making them impermeable to water and other microorganisms. Final Answer The periderm is the plant’s first response to protect itself from freezing, mechanical destruction and disease. The formation of the periderm not only adds girth to the plant but also provides strength and protection to it. The suberin and wax deposits in the cork layer of the periderm are responsible for the toughness of the plant.
