(N/A) $\Rightarrow$ In a maize leaf,a group of $5$ to $7$ large,thin-walled cells without chloroplasts and cuticle are located at certain intervals in the upper epidermis.
$\Rightarrow$ When atmospheric moisture decreases and dryness increases,these cells lose water and become flaccid. As a result,the leaf lamina curls inward. This reduction in the exposed surface area of the leaf helps in preventing excessive transpiration.
$\Rightarrow$ In a humid atmosphere,these cells absorb water and regain their turgidity,causing the leaf to unroll and become exposed again. Due to this water-absorbing property,they are also known as water-absorbent cells.
$\Rightarrow$ Because these cells facilitate the rolling and unrolling movements of the leaf,they are also referred to as motor cells or mechanical cells.