In which of the plant tissues are guard cells located?

Step 1: Analyze the question You are asked where guard cells are found. Guard cells are the pair of bean-shaped cells that surround a stoma (pore) and control its opening and closing.

Step 2: Explain the concept

• The epidermis is the outermost layer of cells of a leaf or young stem. It protects the plant and reduces water loss.
• Stomata, with their guard cells, are openings in the epidermis. They are found mostly on the lower epidermis of leaves, and in some plants on both surfaces.
• Guard cells are unusual among epidermal cells because they contain chloroplasts. When they take in water they become turgid and bend apart, opening the stoma. When they lose water they become flaccid and the stoma closes.

Step 3: Check each option

• A. Epidermis: Correct. Guard cells are specialized epidermal cells.
• B. Mesophyll: This is the photosynthetic tissue (palisade and spongy layers) inside the leaf. It contains air spaces beneath the stomata, but not the guard cells themselves.
• C. Vascular bundles: These are the xylem and phloem, which transport water and food. They do not contain guard cells.
• D. Meristems: These are regions of actively dividing cells at growing tips. They do not contain guard cells.

Step 4: Answer Guard cells are located in the epidermis, which is option A. (The option is spelled "Epidemis" in the question, but "epidermis" is what it means.)

Exam tip: Remember "Guard cells guard the gate in the skin." Stomata are holes in the epidermis, which is the leaf's skin, and guard cells are what open and close them. If you see "stomata" or "guard cells" in a question, think of the epidermis.