What are the protective tissues in plants? Explain details in suitable examples.
Hint: Protective tissues are generally present in the outermost layer of the plant body such as leaves, stem, and roots, and offer safety to the plant body. They stop desiccation, mechanical injury, and infection in plants.
Complete answer: The protective tissues in plants consist of epidermis and cork (phellem).
> Epidermis: It is the outer covering of cells in plants. It carries out protective function (protecting plants from some unfavorable conditions). It is generally made up of a single layer of cells. In arid habitats, the epidermis is thicker to protect the plant from undue loss of water.
> Cork: As plants grow big, a strip of secondary meristem known as cork cambium replaces the epidermis of the stem. It is a plain tissue with only one type of cell. The cork cambium gives off fresh cells on both sides, forming cork. These cells are lifeless with no intercellular spaces and are greatly thickened with suberin. Cork cells avert desiccation, infection, and mechanical injury.
Additional information: On the above-ground parts of the plant, epidermal cells mostly secrete a waxy, water-resistant layer on their outer surface. This waxy layer aids in protecting the plant against loss of water, mechanical injury, and invasion by parasitic fungi. The cells of epidermal tissue are found in a continuous layer devoid of intercellular spaces. Tiny pores are present on the epidermis of the leaf. These pores are called stomata.
Note: The true epidermis is just found in organs got from a cauline vegetative apex, with no checked secondary increment. By and large, epidermal cells structure a continuous layer on the outside of these organs, with no void between their anticlinal dividers, aside from in places where particularly differentiated cells constitute a "stoma".