Mention the exact location of the following:
Guard cells:
Topic: Guard cells
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Pick an option and check your answer. The full worked answer is below either way.
Answer
(d) Around the stoma.
Each STOMA is bounded by two bean-shaped GUARD CELLS, which open and close the pore. They are the only epidermal cells containing chloroplasts.
HOW THEY WORK: when the guard cells take in water they become TURGID. Because their INNER wall (facing the pore) is THICKER and less elastic than the outer wall, they bow outwards as they swell and the pore OPENS. When they lose water they become flaccid, straighten, and the pore CLOSES.
That UNEQUAL THICKENING is the whole mechanism, and it is what examiners want explained — not simply that the cells swell.
Note that the other pores in the plant have no such cells: LENTICELS and HYDATHODES are permanently open and cannot be regulated. Only the stoma can be opened and shut, which is why only it has guard cells.
Around the stoma.