The roots are modified to have root hairs and branch indiscriminately with cells that take in water and nutrients, while the stems are modified to move water and nutrients to and from the leaves and flowers. Stems have nodes with buds where leaves and flowers arise at specific locations, while roots do not.
Roots are adapted to develop root hairs and branch without discrimination, taking in water and nutrients. In contrast, stems are altered to convey water and nutrients between the leaves and flowers. Stems contain nodes with buds that produce leaves and flowers at particular locations, unlike roots which lack such structures.