Question

Thorns of Bougainvillea and phylloclade of Opuntia are modified

• A. leaves
• B. stems
• C. flowers
• D. roots

Answer 1

The correct option is B stems

Thorns of Bougainvillea and phylloclades of Opuntia are modified stems and show homology (similarity in their basic structure but perform very different functions in plants). They are homologous organs.

Thorns of Bougainvillea arise from axillary buds of the stem. Instead of growing into branches, the axillary buds modify to become stiff, sharp structures that protect the plant from grazing animals.


The phylloclade of Opuntia is a flattened green stem that is modified to perform photosynthesis. It acts as a leaf because the leaves in Opuntia are reduced to spines to reduce loss of water by transpiration. The phylloclade bears nodes and internodes which shows that it is a modified stem.


Roots are underground structures that help the plant in anchoring to the soil and absorbing water and minerals from the soil.

Leaves are flattened green structures of the plants and are primarily responsible for photosynthesis.

Flowers are reproductive structures of a plant that attracts the pollinators.