Question

In grasses, certain adaxial epidermal cells along the veins modify themselves into large empty, colourless cells. These cells are called

• A. Bulliform cells
• B. Companion cells
• C. Guard cells
• D. Subsidiary cells
• E. Albuminous cells

Answer 1

The correct option is A Bulliform cells

Bulliform cells are so called because of its peculiar bubble shape. It mainly occurs on the upper surface of the leaves present in grasses. Water present in these cells helps to maintain its shape but loss of turgor pressure during the stress allows the leaves to roll up. 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.

Companion cells are specialized parenchyma cell, located in the phloem of flowering plants and closely associated with development and function with a sieve-tube element.

Guard cells are cells surrounding each stoma. They help to regulate the rate of transpiration by opening and closing the stomata.

The stoma is protected by subsidiary cells that have papillae that arch across the stoma, creating a mini-depression. This will tend to retain escaped water, giving it time to diffuse back into the stoma instead of being immediately blown away by a breeze.

Albuminous cells have a similar role to companion cells, but are associated with sieve cells only and are therefore found only in seedless vascular plants and gymnosperms.

So, the correct answer is option A.