Key Difference – Rhizome vs Tuber
Both rhizome and tuber are two types of specialized stems that contain stem tissues like xylem (conducts minerals and water transportation within the plant), and phloem (conducts food transportation within the plant), but there exist some differences between them based on their appearance and growth. However, both rhizomes and tubers have a culinary value and are commonly consumed in raw or cooked form. If we look at the key difference between rhizome and tuber, rhizome is the underground main stem that runs horizontally to the soil surface while tuber can be a tip of the underground branches of the stem or underground root that stores the food in the form of starch. Tubers share many similarities with rhizomes, but they do have some distinct differences. The purpose of this article is to highlight the different characteristics of rhizome and tuber.
What is a Rhizome?
The entire main stem of the rhizome is under the ground, and it grows in a horizontal direction, spreading from one plant to another. Commonly, rhizome may lie on the soil surface or just below the soil surface. The real appearance and organization of rhizomes may vary from plant to plant. It creates aerial branches that come up for photosynthesis at periodic intervals and often sends roots and shoots from its nodes. Rhizomes are also known as creeping rootstalk or rootstocks. The rhizome can store starches, proteins, as well as other nutrients which become beneficial for the plant when new shoots must be created under drastic climatic conditions. This process is also recognized as vegetative reproduction. Turmeric, Ginger, asparagus, and canna are the best examples for rhizome.
What is a Tuber?
Tuber is a modified, enlarged plant part that stores food mainly in the form of starch to be used for renewal, growth, and/or propagation. Tubers can be defined as the structures derived from stems or roots. Therefore, there are two types of tubers including stem tuber and root tuber. Potato is the best example for a stem tuber. In potatoes, the tip of the underground branches of the stem stores food in the form of starch. Sweet potato is the best illustration for root tuber where subversive root stores the food in the form of starch. Although, tuberous roots are similar to stem tubers, they are actually enlarged roots. Tubers are used by plants to survive the bad climatic conditions such as winter or dry months, deliver energy and nutrients for regrowth during the subsequent growing season and as a source of asexual reproduction.
What is the difference between Rhizome and Tuber?
Definition of rhizome and tuber
Rhizome: Rhizome is a continuously growing horizontal underground stem which puts out lateral shoots and adventitious roots at intervals.
Tuber: Tuber is a much thickened underground part of a stem.
The differences between rhizome and tuber can be divided into following categories. They are;
Growth Habit
Rhizome: Rhizomes grow horizontally.
Tubers: Tuber do not have a well-ordered/organized growing habit, they also do not have a standard shape.
Morphological Features
Rhizome: The nodes of a tuber can develop roots and shoots from its nodes. It’s morphology is similar to human fingers, and it is not enlarged than tubers.
Tubers: The nodes of a tuber can develop into both roots and stems. The tuber has all the parts of a normal stem, including nodes and internodes. Tubers are usually oval, round or conical in shape, and they are larger in size than rhizomes.
Representative Plant Part
Rhizome: Rhizome is the underground stem
Tubers: Tuber is the underground branches of the stem or underground root
Starch Composition
Rhizome: Rhizome contains low starch content compare to tubers.
Tubers: In general, tubers are high in starch.
Types of Rhizome and Tuber
Rhizome: Predominant classification cannot be found in Rhizomes.
Tubers: Two types of tubers; stem and root tubers. A stem tuber is an underground enlarged stem. Potatoes, tuberous begonia, yams, and Cyclamen usually grow as stem tubers. A tuberous root or root tuber is a modified horizontal root. It is, therefore, dissimilar in origin but similar in function and appearance to a stem tuber. Examples of tuberous roots include the sweet potato, cassava, and dahlia.
Examples of Rhizome and Tuber
Rhizome: Bamboo, the Venus Flytrap, Chinese lantern, lotus, Western poison-oak, hops, asparagus, ginger, irises, Lily of the Valley, Cannas, and sympodial orchids, turmeric, galangal, Alstroemeria, Johnson grass, bermuda grass, purple nut sedge and finger root
Tubers: Potato, sweet potatoes, yams, Tuberous begonia, carrot, taro, cassava, and dahlia, Cyclamen, caladiums, oxalis, and anemones
In conclusion, both rhizome and tubers are underground parts of plants adapted for the storage of food materials. The crop survives unfavorable seasonal conditions and they provide the food reserves enabling the plant to make quick growth when conditions are desirable. However, the most noticeable distinguishing feature of rhizomes is their growth habit; they grow horizontally on the soil.
References Rayirath, Usha, P. (2011). Role of ethylene and jasmonic acid on rhizome induction and growth in rhubarb (Rheum rhabarbarum L.). Plant Cell Tissue Organ Culture, 105: 253–263. Mauseth, James, D. (2012), Botany, An Introduction to Plant Biology (5th ed.), Sudbury, MA: Jones and Bartlett Learning, ISBN 978-1-4496-6580-7, p. 672. Martin, FW and Ortiz, Sonia (1963). Origin and Anatomy of Tubers of Dioscorea Floribunda and D. Spiculiflora. Botanical Gazette, 124 (6): 416–421. Davis, P.H. and Cullen, J. (1979), The identification of flowering plant families, including a key to those native and cultivated in north temperate regions, Cambridge: Cambridge University Press, p. 102, ISBN 0-521-29359-6. Image Courtesy: “Ipomoea batatasL ja01”. (CC BY-SA 3.0) via Commons
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