Leaves of many grasses are capable of folding and unfolding because they

Options

A. their mesophyll is not differentiated into palisade and spongy parenchyma
B. they have stomata on both sides of the leaf
C. they have high levels of silica
D. they have specialised bulliform cells

Answer

D

Explanation

Bulliform cells are large, bubble-shaped epidermal cells that occur in groups on the upper surface of the leaves of many grasses. These cells, by their turgor changes, cause rolling and unrolling of the leaves thus regulating water loss.