mention the modified function , performed by:- (1) underground stem of potato. (2) auxillary bud of bougainvilla

1. The underground stem of potato gets modified to store of food.  It also act as organs of perennation to help the plants survive in unfavourable conditions.

​​2. The axillary buds of Bougainvillea get modified into pointed, straight thorns which arise to provide protection to plant from animals.