In which of the following, flowers exhibit both radial and bilateral symmetry?

Question

Accepted Answer

The correct option is 2: Sunflower

The **Sunflower** (*Helianthus annuus*) is the correct answer because it is not a single flower, but an **inflorescence**—a compound structure called a **capitulum** or head—which is composed of two different types of small flowers called **florets**. This composite nature is the key to exhibiting both types of symmetry simultaneously. The outer florets, known as **ray florets**, are large, sterile, and typically have a ligulate (strap-like) corolla. Due to their structure, which allows them to be divided into two mirror-image halves in only one vertical plane, they are an example of **bilateral symmetry (zygomorphic)**. In contrast, the much smaller, central florets, known as **disc florets**, are tubular and fertile. These florets can be divided into two equal halves by any vertical plane passing through the center, a defining characteristic of **radial symmetry (actinomorphic)**. Therefore, the entire sunflower head showcases both radial and bilateral symmetry within its single structure.

The incorrect option is 1: Hollyhock

The **Hollyhock** (*Alcea rosea*) is a member of the Mallow family (Malvaceae), and its flowers are an example of a simple, single-flower structure. The corolla (petals) of a typical hollyhock flower are arranged in a regular, circular pattern around the center. This arrangement means the flower can be divided into two equal and symmetrical halves along *any* vertical plane passing through its center. Therefore, the hollyhock flower exhibits only **radial symmetry (actinomorphic)** and does not contain the specialized florets necessary for dual symmetry.

The incorrect option is 3: Garden Pea

The flowers of the **Garden Pea** (*Pisum sativum*) are structurally distinct and are a classic example used in botany to illustrate **bilateral symmetry (zygomorphic)**. Pea flowers are "papilionaceous," resembling a butterfly, which is characteristic of the Fabaceae (legume) family. They consist of five distinct petals: a large posterior standard (or vexillum), two lateral wings (or alae), and two fused anterior petals that form the keel (or carina). Due to this unique, asymmetrical arrangement, the flower can only be divided into two equal halves along a single, specific vertical plane.

The incorrect option is 4: Marigold

The **Marigold** (*Tagetes* spp.) belongs to the same plant family as the Sunflower, Asteraceae (the Composite family), and is also an inflorescence (capitulum) made up of ray and disc florets. Like the Sunflower, it structurally possesses both zygomorphic (ray florets) and actinomorphic (disc florets) components. However, in the context of this specific multiple-choice question where only one answer can be correct, the Sunflower is traditionally the more definitive and frequently cited example of this dual-symmetry phenomenon. Furthermore, while the general principle of the composite head is the same, the question asks for a single, correct example from the list, and the Marigold's common varieties can sometimes have a less pronounced distinction in their floral structures than the classic single-head sunflower.