What is periderm and protoderm and where do they originate from in a new plant ?

Periderm is the corky outer layer of a plant stem which the plant creates as a result of an injury or infection so as to protect itself further. Protoderm is the thin layer which covers embryos, as well as the root and stems, and later produces epidermis, which is the outer layer of tissue of plants (anywhere where periderm doesn't cover them).