Question

how is stem different from stem tuber

Answer 1

Stem tubers. A stem tuber forms from thickened rhizomes or stolons. The top sides of the tuber produce shoots that grow into typical stems and leaves and the under sides produce roots. They tend to form at the sides of the parent plant and are most often located near the soil surface.

Answer 2

stem is the part of plumule of embryo. It has nodes and internodes. But stem tuber is the underground stem modification of Solanum tuberosum ( potato)