Rhizome
Rhizome and Tuber are both modified stems of a plant and store food but they are both different from each other in many ways. The experts at Vedantu have created a summary of the difference between rhizome and tuber for the students of Biology. Let’s look in detail at these two parts of the plant first.
Rhizomes are underground and horizontal stems that have fleshy, non-green, and distinct nodes and internodes. Rhizomes resemble the root of a plant. They are brownish because they are away from the sunlight. Rhizomes have terminal buds and they run parallel to the ground. New plants can sprout from the buds on a rhizome. They are also known as root stalks and the rhizome root stalk grows vertically upwards. Some common examples of rhizomes are ginger and Alocasia indica
What are the Major Types of Rhizomes?
The rhizomes are mainly of two types, dense rhizomes, and running rhizomes. Dense rhizomes are the ones that grow vertically as roots are produced on the lower side and the shoots grow vertically upright from the nodes whereas running rhizomes are the ones that grow horizontally and can grow underground, subterranean, or above the soil. The horizontal growth is because of the fact that the roots and shoots in running rhizomes grow from the nodes only. Dense rhizomes have short internodes while the long internodes are present in running rhizomes. An example of a dense rhizome is ginger while the example of a running rhizome is bamboo.
What are the Characteristics of Rhizomes?
The main characteristics of rhizomes include:
They allow plants to reproduce through asexual reproduction as well. Plants having rhizomes like ginger and bamboo reproduce through asexual reproduction, that is, vegetative propagation only.
Usually, water plants contain a single stem (rhizome) which is hidden beneath the leaves and flowers.
Rhizome stores food in the form of starch, for example, ginger and turmeric.
These rhizomes store food, thereby, ensuring the growth, development, and survival of plants in adverse winter conditions.
Some rhizomes store energy in the form of starch and sugar grows beneath the ground and has thicker stems as compared to the other rhizomes growing above the ground.
Rhizomes also aid in protecting the perennial plants by providing them with energy throughout the winters.
The advanced stems may have weed characteristics that spread it throughout the place with rapid growth.
Examples of Rhizomes
Rhizomes are majorly of three types, the underground rhizomes, the rhizomes above the ground, and multi-layered rhizomes.
Underground stem rhizomes are very common and are majorly consumed by humans, for example, bamboo, ginger, grass species, hops, and poison oak.
Above the ground rhizomes are the ones that grow close to the soil but not underneath the soil, for example, ferns and irises.
The multi-layered stem system of rhizomes forms both roots and shoots in several layers from the nodes. Such plants have whorls and different layers of leaves, for example, giant horsetails.
Are Rhizoids and Rhizomes the Same Thing?
No, though the words sound very similar the rhizoids and rhizomes are not the same things. Rhizoids are a part of fungi and non-flowering plants like liverworts, hornworts, and mosses. Rhizomes refer to the modified stems that are grown in a horizontal manner continuously and are generally present underground. Rhizoids can either be unicellular or multicellular but rhizomes are only multicellular. The major function of rhizoids is to absorb nutrients, minerals, and water from the soil whereas the major function of rhizomes is to store food in the form of starch and aid in the vegetative reproduction of the plant. Rhizoids are present in most non-vascular plants like algae and bryophytes whereas rhizomes are present in vascular plants only.
Tubers
Although ‘tuber ‘ is a term that generally denotes any fleshy part, in this case, tubers are the fleshy stem of the plant that stores food. In other words, they are the underground part of the branches that become swollen because of the food that gets stored in them. Unlike rhizomes, tubers grow vertically underground. One of the most common examples of a tuber is a potato that is also used as food. Tubers have several depressions called the eyes and they act as nodes for the tuber. Most tubers are spherical, oval, or oblong.
Let’s See Some of the Other Points of Difference Between Tuber and Rhizome
FAQs on Difference Between Rhizome and Tuber
1. What is the main difference between a rhizome and a tuber?
The main difference lies in their shape and method of growth. A rhizome is a horizontal, elongated underground stem that grows parallel to the ground and has distinct nodes and internodes. In contrast, a tuber is a swollen, terminal part of an underground stem that is typically rounded or irregular in shape and stores a large amount of food. A key distinguishing feature is that rhizomes can grow from any node, while tubers sprout new plants from specific points called 'eyes'.
2. Why are both rhizomes and tubers considered modified stems and not roots?
Despite growing underground, both rhizomes and tubers are botanically classified as stems because they possess characteristic stem features that roots lack. These include:
- Nodes and Internodes: They have distinct nodes (points where leaves or buds arise) and internodes (the sections between nodes).
- Scale Leaves: They have small, non-photosynthetic scale leaves at the nodes.
- Axillary Buds: They possess axillary buds (like the 'eyes' of a potato) from which new shoots and roots can grow.
3. What are some common examples of plants with rhizomes and tubers?
Common examples help illustrate the difference.
- Rhizome examples: Ginger (Zingiber officinale), Turmeric (Curcuma longa), Lotus (Nelumbo nucifera), and many types of ferns and irises.
- Tuber examples: The most well-known example is the Potato (Solanum tuberosum). Other examples include Yams (Dioscorea species) and Jerusalem artichoke (Helianthus tuberosus).
4. How can you visually distinguish a rhizome from a tuber?
You can identify them based on a few visual cues:
- Shape: A rhizome is typically elongated, cylindrical, or irregularly branched, growing horizontally. A tuber is generally a swollen, fleshy, and rounded structure.
- Bud Location: On a rhizome, buds that can form new shoots appear along its length at the nodes. On a tuber, these buds are clustered in depressions known as 'eyes'.
- Growth Pattern: Rhizomes are main stems that grow continuously underground, while tubers are typically the swollen tips of underground branches.
5. Is a carrot considered a rhizome or a tuber?
A carrot is neither a rhizome nor a tuber. It is a type of modified taproot. Unlike rhizomes and tubers, which are modified stems, a carrot is the primary root of the plant that has become swollen to store food, primarily sugars. It lacks the nodes, internodes, and scale leaves that characterize stems.
6. How do rhizomes help in vegetative propagation?
Rhizomes are highly effective for vegetative propagation. The horizontal stem grows underground, and new shoots can emerge upwards from the nodes while roots grow downwards. If a piece of the rhizome containing at least one node is separated from the parent plant, it has the ability to grow into a new, genetically identical plant. This allows the plant to spread rapidly and survive unfavorable conditions.
7. Are potatoes and sweet potatoes both tubers?
No, this is a common misconception. While they both are underground storage organs, they have different botanical origins. A potato is a stem tuber, meaning it is a modified stem. A sweet potato is a tuberous root, meaning it is a modified root. You can tell the difference because a potato has 'eyes' (nodes), whereas a sweet potato does not and will sprout roots and shoots from any point on its surface.
8. What is happening botanically when a potato develops 'eyes' or sprouts?
The 'eyes' on a potato are actually its nodes. Each eye contains one or more axillary buds. When conditions like warmth and humidity are suitable, these buds break their dormancy and begin to grow, using the stored starch in the tuber as energy. This process, called sprouting, is the beginning of vegetative propagation, where each sprout can potentially grow into a new potato plant.
9. What is the primary function of a tuber in a plant's life cycle?
The primary function of a tuber is to act as a food and water storage organ. By storing nutrients, mainly in the form of starch, the tuber helps the plant survive periods of dormancy, such as winter or a dry season. When favorable conditions return, the plant uses these stored energy reserves to fuel the growth of new shoots, ensuring its survival and propagation.
