Question

leaves are absent in a cactus plant -- state true or false and why

Answer 1

Leaves are absent in cactus plant,they modified into spines .

Mosts of cacti have lost true leaves, retaining only spines, which are highly modified leaves. As well as defending against herbivores, spines help prevent water loss by reducing air flow close to the cactus and providing some shade. In the absence of leaves, enlarged stems carry out photosynthesis.
The great majority of cacti have no visible leaves; photosynthesis takes place in the stems (which may be flattened and leaflike in some species).