What is the Difference Between Racemose and Cymose Inflorescence

The key difference between racemose and cymose inflorescence is that racemose inflorescence is a type of inflorescence where the main axis has continuous growth and flowers are present laterally, while cymose inflorescence is a type of inflorescence where the main axis has limited growth and flowers are present terminally.

Inflorescence is a type of flower arrangement in flowering plants. It has a cluster of flowers arranged on a stem or a floral axis. There are two types of inflorescence based on the growth of the floral axis. They are racemose and cymose inflorescence. In racemose inflorescence, the flowers are arranged laterally in an acropetal manner, and the main axis or stem continues to grow indefinitely. In cymose inflorescence, the main axis or stem terminates into a flower and therefore has a limited growth or determinate growth. In addition, there are several other types of inflorescences like compound inflorescence, cyathium, hypanthodium, and verticillaster.

CONTENTS

1. Overview and Key Difference
2. What is Racemose Inflorescence
3. What is Cymose Inflorescence
4. Similarities – Racemose and Cymose Inflorescence
5. Racemose vs Cymose Inflorescence in Tabular Form
6. Summary – Racemose vs Cymose Inflorescence

What is Racemose Inflorescence?

Racemose inflorescence is a type of inflorescence where the main axis has unlimited growth. Racemose inflorescence contains a peduncle as the main axis, and this continues to produce a flower bud. However, the peduncle rarely terminates in flower. It is monopodial, i.e., it contains a single main stem that produces leaves and flowers. The initial flowers that are formed form at the base of the peduncle and are borne laterally in an acropetal arrangement. Generally, younger flowers arrange in the tip or middle, and older flowers are at the periphery or at the base.

Racemose inflorescence divides into various types such as raceme, spike, spikelets, catkin, spadix, corymb, umbel, and capitulum based on branching, peduncle length, and presence or absence of pedicel. Raceme, spike, spikelets, catkin, and spadix have an elongated main axis. Corymb and umbel have a shortened main axis. The capitulum has a flattened main axis. Raceme consists of a main axis that is unbranched and elongated and bears pedicellate flowers in an acropetal arrangement. The main axis of the spike is also unbranched with unlimited growth, but flowers are sessile. Spikelets are compound spikes, and they are branched with sessile flowers. Catkin is a modified version of a spike with a drooping central stem and has sessile flowers that are unisexual. Spadix is also a modified version of a spike with a fleshy axis and contains a number of sessile flowers. Corymb has a branched main axis and contains pedicellate flowers. Each branch has flowers arranged in corymbs. Umbel contains a whorl, and flowers arise from the axil of bracts. Capitulum is called the racemose head. It is the most advanced inflorescence. The peduncle is short and broad, and the flowers are known as florets.

What is Cymose Inflorescence?

The cymose inflorescence is a type of inflorescence characterized by the presence of a flower at the apex of the floral axis. This inflorescence contains a lateral axis that terminates into flowers and limits the growth of the axis. The flowers present are in basipetal arrangement; younger flowers are at the base, and older flowers are in the tip or middle.

There are four main types of cymose inflorescence: monochasial cyme, dichasial cyme, polychasial cyme, and cymose capitulum. Monochasial cyme is also known as uniparous cyme, and its main axis terminates in flowers. This also produces a lateral branch from the base with a terminal flower. Monochasial cyme is further divided into two types: scorpioid and helicoid. Dichasial cyme is also known as the biparous cyme, and the terminal peduncle terminates in the flower. This gives rise to two lateral branches with terminal flowers. Polychasial cyme is known as the multiparous cyme and has multiple branches that arise at the base of the apical flower of the peduncle. The peduncle reduces to a circular disc. Here, the older flowers develop in the centre while the younger flowers develop in the periphery.

What are the Similarities Between Racemose and Cymose Inflorescence?

• Racemose and cymose inflorescence are types of arrangement of flowers.
• Both are simple inflorescences.
• Both have a number of florets arranged in a common peduncle.
• Attachment of floret to peduncle occurs through a pedicel in both types.
• The main function of both is to enhance cross-pollination.

What is the Difference Between Racemose and Cymose Inflorescence?

In racemose inflorescence, the flowers are arranged laterally, while in a cymose inflorescence, the flowers are arranged terminally on the floral axis. Thus, this is the key difference between racemose and cymose inflorescence. Also, racemose inflorescence shows a continuous growth in the main floral axis, but cymose inflorescence shows a limited growth in the main floral axis. Moreover, the peduncle in racemose inflorescence shows a monopodial growth, while in a cymose inflorescence, the peduncle shows a sympodial or multipodial growth.

The below infographic presents the differences between racemose and cymose inflorescence in tabular form for side by side comparison.

Summary – Racemose vs Cymose Inflorescence

The inflorescence is of two types based on the growth of the apex. They are racemose and cymose. In racemose inflorescence, the flowers are arranged laterally, while in a cymose inflorescence, the flowers are arranged terminally on the floral axis. The main axis of the racemose inflorescence has unlimited growth. It contains a peduncle as the main axis, and this continues to produce a flower bud. The cymose inflorescence has a flower at the apex of the floral axis. The main axis of the cymose inflorescence has limited growth. So, this summarizes the difference between racemose and cymose inflorescence.

Reference:

1. “Cymose Inflorescence: Types, Difference between Racemose and Cymose.” BYJUS, BYJU’S, 31 Mar. 2022.
2. “Racemose Inflorescence: Characteristics, Types, Example.” BYJUS, BYJU’S, 30 Mar. 2022.

Image Courtesy:

1. “Caesalpinia pulcherrima at Kadavoor” By © 2009 Jee & Rani Nature Photography (CC BY-SA 4.0) via Commons Wikimedia
2. “Inflorescences multiCyme Kwiatostan Wierzchotka” By Shazz – Own work (CC BY-SA 3.0) via Commons Wikimedia