Question

why are the leaves of the cactus plant reduced to spines

Answer 1

The leaves of a cactus have become spines to limit the loss of water through transpiration. The plant has to prevent water loss as there is very little rainfall in the areas of the cactus.

Answer 2

The leaves of 'cactus' are reduced to 'spines' to prevent the loss of water by transpiration.

EXPLANATION:

Leaves lose water by the process of transpiration but cactus grows in deserts and cannot afford to lose water.

The spines of the cactus store water. They reduce air flow around cactus and help the plant to get enough water by storing it. The stems and not the leaves of the cactus contain chlorophyll to prepare food.