Identify the given figure:

Stem thorns help in

Describe the modifications of the stem for protection.

$A$ weak creeping stem,rooting at nodes and bearing a series of plants of successive vegetative generations is called:

In $Opuntia$,the stem is modified into a flattened green structure to perform the function of leaves (i.e.,photosynthesis). Cite some other examples of modifications of plant parts for the purpose of photosynthesis.

Which is not a modification of stem?