What is the Difference Between Calyx and Corolla

The main difference between calyx and corolla is that calyx is the whorl of sepals of a flower whereas corolla is the whorl of petals. Furthermore, calyx forms the outermost layer of the flower while corolla is the whorl that occurs in the inner side of the calyx.

Calyx and corolla are two whorls of modified leaves, serving as the structures of a flower. They are collectively known as the perianth. Moreover, calyx protects the internal structures of the flower bud while corolla attracts pollinators to the flower.

Key Areas Covered

1. What is the Calyx
     – Definition, Structure, Function
2. What is the Corolla
     – Definition, Structure, Function
3. What are the Similarities Between Calyx and Corolla
     – Outline of Common Features
4. What is the Difference Between Calyx and Corolla
     – Comparison of Key Differences

Key Terms

Calyx, Corolla, Flower, Petals, Pollinators, Sepals

What is the Calyx

The calyx is the collection of sepals of a flower, mainly appearing in green color. They are smaller and leaf-like. Generally, the calyx forms a hard structure, which protects the inner structures of the flower bud from mechanical injuries and desiccation. In addition, after blooming, it forms the outermost layer of the flower, supporting the petals and the reproductive structures. The calyx also protects the developing fruit, even after the fall of petals and other reproductive structures of a flower.

Figure 1: The Calyx of Brugmansia aurea

Furthermore, the form and the development of the calyx widely vary among flowers. Some calyxes have freely-occurring sepals known as polysepalous calyx while other calyxes have fused sepals to form a calyx tube known as gamosepalous calyx. Moreover, the sepals and petals of some flowers have the same color and size, making them indistinguishable from each other. These are known as tepals. The main function of tepals is to attract pollinators to the flower.

What is the Corolla

The corolla is the collection of petals of the flower with bright colors to attract pollinators such as insects, birds, etc. They are large but, delicate structures. The whorl of petals occurs inside the calyx and it protects the reproductive structures of the flower, including the stamen and pistil. Moreover, the number of petals in a flower is the main characteristic features that can be used to classify the flower. Eudicot flowers typically have four or five petals in their corolla while monocot or palaeodicot flowers have three petals or a multiple of three.

Figure 2: The Corolla of Geranium incanum

Just like the calyx, the form and the development of the corolla widely vary among flowers. Usually, many flowers are symmetrical only in one particular plane. Moreover, some flowers contain all symmetrical petals while others contain asymmetrical petals. Different flowers have different sizes and shapes of blades. Also, some petals are fused together by their petioles or even by their blades, forming a tube.

Similarities Between Calyx and Corolla

• Calyx and corolla are the two outermost whorls of a flower, collectively forming the perianth.
• They surround the reproductive structures of the flower: stamen and pistil.
• Moreover, both are modified leaves.
• Also, they are non-reproductive structures responsible for protecting the reproductive structures of the flower.
• Additionally, merosity is the number of sepals or petals in a flower used to classify flowers.

Difference Between Calyx and Corolla

Definition

Calyx refers to the sepals of a flower, typically forming a whorl, which encloses the petals and forms a protective layer around a flower in the bud, while corolla refers to the petals of a flower, typically forming a whorl within the sepals and enclosing the reproductive organs. Thus, this is the main difference between the calyx and corolla.

Known as

The whorl of sepals of a flower is known as the calyx while the whorl of petals is known as the corolla.

Occurrence

Calyx forms the outermost layer of the flower while corolla occurs inside of the calyx, surrounding the reproductive structures.

Color

Generally, the calyx is green in color while the corolla has bright colors.

Structure

Their structure is a major difference between the calyx and corolla. The calyx is leaf-like while the corolla is petaloid.

Size

Usually, the sepals of the calyx are small while the petals of the corolla are large.

Texture

Another difference between the calyx and corolla is that the calyx is a hard structure while the corolla is a more delicate structure.

Function

Moreover, the calyx protects the inner structures of the flower bud while the corolla attracts pollinators to the flower.

In Absence

Flowers without a calyx are known as asepalous while flowers without a corolla are known as apetalous.

Conclusion

The calyx is the outermost whorl of the flower, consisting of sepals. Generally, sepals are small and leaf-like. They are also green in color. The main function of the calyx is to protect the internal structures of the flower bud. On the other hand, corolla is the whorl of petals, which occurs inside the calyx and surrounds the reproductive structures of the flower. Usually, the petals of the corolla are large and have bright colors to attract pollinators to the flower. However, both calyx and corolla collectively form the perianth of the flower. The main difference between the calyx and corolla is their structure and function.

References:

1. Nelson, Randal C. “The Description of Flowers.” Flower Description Glossary, Available Here.

Image Courtesy:

1. “2007 brugmansia aurea” By Rl – Own work (CC BY-SA 3.0) via Commons Wikimedia   
2. “Geranium incanum 9156s” By JonRichfield – Own work (CC BY-SA 3.0) via Commons Wikimedia