What Is the Difference Between a Corm and a Bulb in Structure and Function
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A Gladiolus corm and an onion bulb
What are Corms and Bulbs?
The stem is modified into various forms in different plants to suit their adaptation needs. These modifications can be underground, aerial, or even sub-aerial. Underground modifications of stems consist of rhizomes, bulbs, corms, and tubers. They may resemble the plants' roots, but they differ in the presence of nodes and internodes, leaves, and buds. The main reason for the development of stem modifications is to allow the plant to survive in all kinds of environments and habitats, which are distinct from the regular ones.
Nature has modified stems and made them capable of performing the functions of food storage, plant support, protection, and vegetative propagation. These types of plants come under the category of Geophytes. Both corms and bulbs need a rest period that follows a time of active growth. Garlic is an example of a bulb, while corm examples are crocus, gladiolus, autumn crocus, etc.
Let us study two such underground stem modifications, the corm, and the bulb, and the difference between corm and bulb.
What is a Corm?
A corm is a swollen, underground plant stem modification that is present in some plants. Corms are built for nutrients and food that the plant can use in due course of time. These nutrients are generally stored in the corm during one growing season. They help produce various parts of the plants, like, roots, leaves, and flowers, for the next growing season of the plant.
Corms look similar to bulbs but are different from them as they do not possess the layered scales present in the bulbs. Corms reproduce via cormlets or individual corms. These cormlets can be separated from the parent to produce exact copies of the plant.
Corms are flattened or slightly round in appearance. Roots can grow from the corm base under the soil. In most cases, the parent corm dies back, and the corm lets it become the source of the plant the next year. The corm has membranous to scaly leaves and absorbs nutrients. It stores them for the next season. The corm can be divided and transplanted into other areas of the garden for vegetative propagation. Gladiolus, crocus, and crocosmia are classic corm examples.
What is Bulb?
A bulb is another stem modification. Most perennial monocotyledons have this form of a stem that provides a resting stage to their seeds. A bulb has a large, central bud that grows underground and is usually globe-shaped. The center of the bulb contains a bud that produces leaves and flowers. It also has membranous or fleshy leaves that arise from a short stem. A cluster of adventitious roots arises from the bulb base. The lateral buds give rise to shoots of the bulb. The plant’s food is stored in the leaves. New bulbs replace the old bulbs as they grow.
Onion is the best example of a bulb, apart from garlic. Lily plants, tulips, and hyacinths are also bulb plants. Some bulbs are grown for their decorative flowers, like, lily, tulip, and iris.
Difference Between Corm and Bulb
Now that we know what is a corm and a bulb and how they store food let us try to distinguish between the two. The table given below provides the difference between corm and bulb.
Fun Facts
The largest corm is that of Titan Arum that weighs more than 150 kg.
FAQs on Difference Between Corm and Bulb in Plants
1. What is the main difference between a corm and a bulb?
The main difference between a corm and a bulb is that a corm is a solid, swollen underground stem, while a bulb consists of layered fleshy leaves surrounding a central bud.
- Corm: Solid inside, made of stem tissue (e.g., gladiolus).
- Bulb: Has concentric layers (scales) that store food (e.g., onion, lily).
- Corms are covered by dry, papery scale leaves, while bulbs have visible fleshy layers when cut open.
2. What is a corm in plants?
A corm is a short, vertical, swollen underground stem that stores food to help a plant survive unfavorable conditions.
- It is made of solid stem tissue.
- Covered with dry, scaly leaves called tunics.
- Produces roots from the base and shoots from the top.
3. What is a bulb in plants?
A bulb is an underground storage organ made of a short stem surrounded by thick, fleshy storage leaves.
- The central part contains a growing bud.
- The fleshy scales store nutrients.
- It is enclosed by a protective outer covering called a tunic (in tunicate bulbs).
4. How can you tell the difference between a corm and a bulb by cutting them open?
You can distinguish a corm from a bulb by observing their internal structure when cut open.
- A corm appears solid and uniform inside.
- A bulb shows distinct concentric layers or rings.
- The layered structure of bulbs represents fleshy storage leaves.
5. What are examples of corms and bulbs?
Examples of corms and bulbs differ based on their underground stem structure.
- Corms: Gladiolus, crocus, taro.
- Bulbs: Onion, garlic, lily, tulip.
6. Are corms and bulbs both modified stems?
Yes, both corms and bulbs are types of modified underground stems used for storage and perennation.
- Corm: Swollen stem base storing food in solid stem tissue.
- Bulb: Short stem with fleshy leaves attached to it.
- Both help plants survive adverse seasons like winter or drought.
7. What is the function of a corm and a bulb?
The primary function of both corms and bulbs is food storage and vegetative reproduction.
- Store carbohydrates and nutrients.
- Help the plant survive unfavorable conditions.
- Produce new shoots during the growing season.
8. Do corms and bulbs reproduce vegetatively?
Yes, both corms and bulbs reproduce through vegetative propagation by forming new daughter structures.
- Corms produce small cormels around the parent corm.
- Bulbs form bulblets or daughter bulbs.
- These develop into genetically identical plants.
9. Is onion a corm or a bulb?
Onion is a bulb because it consists of fleshy layered leaves attached to a short stem.
- It shows concentric rings when cut open.
- The layers store nutrients.
- It is a classic example of a tunicate bulb.
10. Why are corms often confused with bulbs?
Corms are often confused with bulbs because both are underground storage organs with similar appearance and function.
- Both grow below the soil surface.
- Both store food and produce new shoots.
- Both may have a papery outer covering.
