Difference Between Stem Tuber and Root Tuber

The main difference between stem tuber and root tuber is that the stem tuber is a swollen stem whereas the root tuber is a swollen root. For example, potatoes are stem tubers while dahlias are root tubers. 

Stem tuber and root tuber are two types of tubers swollen by storing water and nutrients. Tubers, when compared to the other geophytes such as bulbs, corms or rhizomes, do not produce an offset but, grow in size in every year. 

Key Areas Covered 

1. What is a Stem Tuber
     – Definition, Facts, Examples
2. What is a Root Tuber
     – Definition, Facts, Examples
3. What are the Similarities Between Stem Tuber and Root Tuber
     – Outline of Common Features
4. What is the Difference Between Stem Tuber and Root Tuber
     – Comparison of Key Differences

Key Terms 

Chlorophyll, Eyes, Root Tuber, Stem Tuber, Underground Swollen Structures 

What is a Stem Tuber 

Stem tuber is a swollen stem that stores water and nutrients. These nutrients and water are used in unfavorable conditions such as drought or winter months. Stem tubers generally form near the surface of the soil. They have several nodes called eyes that develop into new plants. Also, stem tubers produce chlorophyll when exposed to sunlight.  

Figure 1: Potatoes

What is a Root Tuber 

Root tubers are the swollen roots due to the storage of water and nutrients. They are also called root crops. Root tubers perform the general functions of roots such as the absorption of water and minerals and anchoring the plant body to the soil. Some examples of root tubers are beet, carrot, parsnip, and dahlias. 

Figure 2: Carrots

Carrot has an enlarged taproot. Some root tubers are formed from adventitious roots. 

Similarities Between Stem Tuber and Root Tuber 

• Stem tuber and root tuber are two types of geophytes. 
• Both are underground swollen structures of plants. 
• They store water and nutrients. 
• They anchor plant bodies to the soil. 

Difference Between Stem Tuber and Root Tuber 

Definition 

Stem tuber refers to a short fleshy usually underground stem bearing minute scale leaves, each of which bears a bud in its axil and is potentially able to produce a new plant while root tubers refer to a tuberous root or storage root, which is a modified lateral root, enlarged to function as a storage organ. 

Type of Tuber 

Stem tuber is a swollen stem while root tuber is a swollen root. 

Storage 

Stem tuber can store more starch while root tuber can store comparatively fewer amounts of starch. 

Carbohydrate Composition 

Stem tuber mainly store complex carbohydrates such as starch while root tubers store simple carbohydrates such as glucose. 

Number of Tubers 

Several stem tubers occur per plant while only a single tuber occurs per a plant. 

Apical Bud 

Stem tubers possess an apical bud at the tip while root tubers do not possess an apical bud. 

Development of Chlorophyll 

Stem tubers develop chlorophyll upon exposure to sunlight while root tubers may not develop chlorophyll. 

Scaly leaves and Auxiliary Buds 

Stem tubers possess scaly leaves and auxiliary buds while root tubers do not possess scaly leaves and auxiliary buds. 

Roots 

Stem tubers do not have roots while root tubers have some fine roots. 

Generating New Plants 

Each part of the stem tuber can grow into a new plant when the tuber is cut into parts while the parts of a root tuber cannot develop into new plants.  

Examples

Potatoes are stem tubers while beet, carrot, parsnip, and dahlias are root tubers. 

Conclusion 

Stem tubers are the swollen stems while root tubers are swollen roots. Stem tubers possess several eyes, which develop into new plants. The main difference between stem tuber and root tuber is the plant part which undergoes swelling. 

Reference:

1. “Tuber.” Wikipedia, Wikimedia Foundation, 10 July 2018, Available Here

Image Courtesy:

1. “Food-Root-Nature-3291163” (CC0) via Max Pixel
2. “Carrots” By color line (CC BY 2.0) via flickr