Question

External protective tissues of plants are_______
A. Cortex and epidermis
B. Pericycle and cortex
C. Epidermis and cork
D. Pericycle and cork

Answer 1

Hint: The protective tissues, such as leaves, stems and roots, are typically found in the outermost layer of the plant body and provide protection to the plant body. In plants, they resist desiccation, mechanical damage, and infection. These tissues may be thicker in some plants living in very dry environments, because protection against water loss is important.

Complete answer:
The epidermis is a cell line layer that protects the plants' leaves, buds, roots and stems. A boundary between the plant and the outside environment is recognized. The cork cambium is a tissue used as part of the epidermis of many vascular plants. The cork cambium is a lateral meristem and is responsible for secondary growth in roots and stems that replaces the epidermis.
The pericycle is a cylinder of cells that are just within the endodermis of parenchyma or sclerenchyma and is the external most element of the stele of plants. In plants, the cortex is the tissue of unspecialized cells between the epidermis (surface cells) and the stem and root tissues of the vascular or conducting tissue.
The epidermis and pericycle, with parenchyma or collenchyma cells, gain secondary meristematic property by de-differentiation during extrastellar secondary growth and are referred to as phellogen or cork cambium. The outer layer of this cambium gradually loses its protoplast and becomes dead, thickening its cell walls. These cells comprise cork or phellem.

Hence, the correct answer is option (C).

Note: The cork cells are dead with no intercellular space and compactly wrapped. A waxy substance, suberin, which does not prevent water and gases to move through, coats their cell walls. It also protects the plant against mechanical damage and by evaporation, also prevents water loss. The epidermis is one thick cell and is surrounded by cuticles.