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Protective tissues are usually present in the outermost layer of the plant body such as leaves, stem and roots. It is one cell thick and covered with cutin and protects the underlying tissues present in the plant body.
As roots and stems grow older with time, tissues at the periphery become cork cells. Cork cells are dead, have no intercellular spaces and the cell walls are heavily thickened by the deposition of suberin. They prevent loss of water.
Activity - I
Take a thin layer of tissue from the lower surface of the leaf. Mount it on a slide in water and examine under a microscope. You will find tiny pores or stomata along with the epidermal cells. The stomata are bound by a pair of guard cells whose concave sides face each other. It is through the stomatal opening that transpiration and exchange of gases take place. An active stoma will look like this.
Activity - II
Hold a bottle cork in one hand firmly and cut a thin slice with the help of a blade. Place the section in a drop of water on a glass slide and observe under a microscope. You will find cells, which are box-like and closely packed together.
