Question

The presence of motor cells in the upper epidermis of leaves in grasses is to:

• A. Increase the surface area of the leaf
• B. Store large amount of water
• C. Check transpiration by reducing the surface area of the leaf
• D. Bear unicellular trichomes

Answer 1

The correct option is C Check transpiration by reducing the surface area of the leaf

Bulliform cells or motor cells are large, bubble-shaped epidermal cells that occur in groups on the upper surface of the leaves of many grasses. Loss of turgor pressure in these cells causes leaves to roll up during water stress. During drought, the loss of moisture through vacuoles induces bulliform cells to cause the leaves of many grass species to close as the two edges of the grass blade fold up toward each other. Once adequate water is available, these cells enlarge and the leaves open again. Folded leaves offer less exposure to sunlight, so they are heated less thus, reducing evaporation and conserving the remaining water in the plant and occur on the leaves of many monocotyledons but are probably best known in grasses

So, the correct answer is C.