why stem of a cactus perform the function of a leaf ? Share with your friends Share 0 Sneha Dharshini answered this as the leaf of a cactus is filled up with spines it could not make food -1 View Full Answer Rangona Banerjee answered this IN DESERT PLANTS,THE STEM IS MODIFIED INTO GREEN FLATTENED OR ROUNDED STEM WHICH BEARS MODIFIED LEAVES IN THE FORM OF SPINES TO REDUCE WATER LOSS. E.g- PRICKLY PEAR. 0