What is the Difference Between Racemose and Cymose

The main difference between racemose and cymose is that the growth of the peduncle is indefinite in the racemose inflorescence whereas the growth of the peduncle is definite in the cymose inflorescence. Furthermore, the terminus of the peduncle does not develop into a bud in the racemose inflorescence while the tip of the peduncle develops into a flower.

Racemose and cymose are two types of organizations of inflorescences. Here, an inflorescence is a cluster of flowers arranged on a stem composed of a main branch known as the peduncle with or without a complicated arrangement of branches.

Key Areas Covered

1. What is Racemose Inflorescence
     – Definition, Structure, Types
2. What is Cymose Inflorescence
     – Definition, Structure, Types
3. What are the Similarities Between Racemose and Cymose Inflorescence
     – Outline of Common Features
4. What is the Difference Between Racemose and Cymose Inflorescence
     – Comparison of Key Differences

Key Terms

Acropetal, Basipetal, Cymose, Determinate, Indeterminate, Inflorescence, Racemose

What is Racemose Inflorescence

Racemose is a type of inflorescence with a peduncle of indefinite growth. Therefore, this type of inflorescence is known as infinite or indeterminate inflorescence. On that account, the growing point seldom ends in a flower. Also, the formation of flowers in the racemose type of indefinite.

Figure 1: Racemose Inflorescence of Hoary Plantain

Furthermore, the formation of flowers in the racemose inflorescence is acropetal. That means; the growth of flowers occurs upwards from the base or point of attachment. Also, the peduncle is monopodial. Therefore, the upward growth of the inflorescence occurs starting from a single point. Moreover, the arrangement of flowers is centripetal means the younger flowers occur towards the center while the older ones occur towards the outside.

What is Cymose Inflorescence

Cymose is another type of inflorescence with a peduncle of definite growth. Therefore, it is known as definite or determinate inflorescence. Significantly, the terminus of the peduncle always bears a flower, which becomes the first-formed flower of the inflorescence. On that account, the formation of flowers of a cymose inflorescence becomes restricted.

Figure 2: Cymose Inflorescence of Pelargonium zonale

Also, the formation of flowers in the cymose inflorescence is basipetal. That means; the growth of flowers occurs downwards towards the base or point of attachment. Further, the peduncle is either sympodial or multipodial. Here, one or more lateral meristems respectively become activated with the termination of the apical meristem by the formation of the terminal flower first. In contrast, the arrangement of flowers is centrifugal and the younger flowers occur towards the periphery while the older ones occur towards the center.

Similarities Between Racemose and Cymose Inflorescence

• Racemose and cymose are two types of organizations of inflorescences.
• Both comprise a number of florets arranged in a common peduncle.
• Also, both are two types of simple inflorescences.
• The attachment of each of the floret to the peduncle occurs through a pedicel.
• Moreover, the main function of both is to encourage cross-pollination.

Difference Between Racemose and Cymose Inflorescence

Definition

Racemose refers to a type of flowering shoot in which the growing region at the tip of the flower stalk continues to produce new flower buds during growth while cymose refers to a type of flowering shoot in which the first-formed flower develops from the growing region at the top of the flower stalk. Thus, this describes the fundamental difference between racemose and cymose inflorescence.

The Growth of the Peduncle

Aboveall, the main difference between racemose and cymose inflorescence is that the growth of the peduncle is indefinite in the racemose inflorescence whereas the growth of the peduncle is definite in the cymose inflorescence.

Formation of Flowers

Also, the formation of flowers is indefinite in the racemose inflorescence while the formation of flowers is definite in the cymose inflorescence.  

Type of growth of the Peduncle

Moreover, the peduncle of the racemose inflorescence shows monopodial growth while the peduncle of the cymose inflorescence shows either sympodial or multipodial growth. Hence, this is also an important difference between racemose and cymose inflorescence.

Terminus

Besides, the terminus of the peduncle does not develop into a bud in the racemose inflorescence while the tip of the peduncle develops into a flower in the cymose inflorescence.

Type of Flower Formation

Another difference between racemose and cymose inflorescence is that the formation of flowers is acropetal in the racemose inflorescence while the formation of flowers is basipetal in the cymose inflorescence.

First-Formed Flower

Furthermore, the first-formed flower of the racemose inflorescence occurs at the base of the peduncle while the first-formed flower of the cymose inflorescence occurs at the tip of the peduncle.

Arrangement of Flowers

Arrangement of flowers is also a difference between racemose and cymose inflorescence. That is; the arrangement of flowers in the racemose inflorescence is centripetal while the arrangement of flowers in the cymose inflorescence is centrifugal.

Opening of Flowers

In addition, the flowers open at short intervals in the racemose inflorescence while flowers open at long intervals in the cymose inflorescence.

Grouping of Flowers

And, the grouping of flowers is less common in the racemose inflorescence while the grouping of flowers is more common in the cymose inflorescence.

Protection of Fruits

Newly formed fruits are not protected by the flowers in the racemose inflorescence while the newly formed fruits are protected by the flowers in the cymose inflorescence.

Types

The types of the racemose inflorescence are the raceme, spike, corymb, spadix, etc. while the three main types of cymose are the monochasial cyme, dichasial cyme, and polychasial cyme.

Conclusion

Racemose is a type of inflorescence with a continuously growing peduncle. Therefore, the formation of flowers in the racemose inflorescence is indefinite. Also, the terminus of the peduncle seldom bears a flower bud and the formation of flowers is acropetal. Whereas, cymose is another type of inflorescence with a peduncle of definite growth. Therefore, the formation of flowers in the cymose inflorescence is also definite. Also, it bears a terminal flower bud, which becomes the first-formed flower of the inflorescence. On the other hand, the formation of flowers in the cymose inflorescence is basipetal. Hence, the main difference between racemose and cymose inflorescence is the growth of the peduncle and the method of formation of flowers.

References:

1. “Racemose Inflorescence.” A Dictionary of Biology, Encyclopedia.com, Available Here.
2. “Cymose Inflorescence.” A Dictionary of Biology, Encyclopedia.com, Available Here.

Image Courtesy:

1. “Plantagomedia” (CC BY-SA 3.0) via Commons Wikimedia   
2. “Fiore di geranio” (CC BY-SA 3.0) via Commons Wikimedia