Question

how do vegetables like stem tubers and plump gourd propagate

Answer 1

The vegetables like stem tubers and plump gourds propagate through vegetative propagation. the method of reproduction through vegetative parts is called vegetative propagation. in vegetative propagation they reproduce by underground stem.
           the organs that store food are also the organs for reproduction. they store starch  during the summer months. in autumn, the plants die  but the organs full of stored food remain  underground ( dormant )  and survive the winter. they produce new plants the following year.
hope I helped u !!!!!! 

Answer 2

These vegetables propogate by the method of vegetative propagation.
It means that if a part of the plant body is cut , the cells remain living and multiply to form a new plant.
Example:Rose plant.