Difference between Rhizome and Tuber

The underground stems perform the functions of perennation, storage of food and vegetative propagation.They produce new shoots annually. The underground stem modifications include rhizome, bulb, corm and stem tuber. 

Rhizome: It is stout, dorsoventrally flattened underground stem which creeps horizontally beneath the surface of the ground. It is fleshy due to the storage of food material.

Example: Ginger, Turmeric, Canna etc.

Tuber is a general term that can be applied for any type of fleshy structure. But in the case of stem it is an underground modification where the end of underground branches become swollen due to the storage of food material. It is almost spherical, oblong or oval in shape.
Example: Potato (Solanum tuberosum)

Rhizome vs Tuber

Rhizome

1. Rhizomes are less stouter than tubers.
2. The nodes bear adventitious roots  on the lower side.
3. Buds are present in the axils of scaly leaves and also as terminal buds.

 Tuber

1. Tubers are more stouter than rhizomes. 
2. Nodes do not bear roots. 
3. Buds which are technically known as ‘eyes’ are present on the surface of the tuber. These buds are formed in the axils of small scale leaves.