Which one of the following is a modified stem?

Correct answer: (b) Phylloclade of cactus (*Opuntia*)

Explanation

In *Opuntia* (prickly pear cactus), the stem is flattened, green and fleshy and does the work of the leaves, which are reduced to spines to save water. This leaf-like stem is a phylloclade, a modified stem.

• The pneumatophores of mangroves are modified roots that grow upward to take in air.
• Turnip is a modified (storage) root.
• Cabbage is a large bud: a short stem covered by overlapping leaves; the part we eat is mostly leaves.