Sepals

Sepals are one of the key structural parts of a flower, forming the outermost whorl of floral parts and typically functioning as protection for the flower in bud, and often supporting the petals when in bloom. Sepals are collectively known as the calyx, and individual sepals are usually green and leaf-like, although they can be colorful and petal-like in some species.

Structure and Function

Sepals are typically the first part of a flower to form, arising from the top of the flower stem (pedicel). They enclose and protect the developing bud and may remain after blossoming to support the petals and provide protection to the reproductive structures within. The morphology of sepals can vary significantly between species. In general, they are differentiated from petals by their thicker and more robust structure and their position on the flower, which is usually outermost.

Variations

In some plants, sepals are fused together forming a structure known as a gamosepalous calyx, while in others, they are free (polysepalous). Sepals can sometimes be difficult to distinguish from petals, especially in flowers that have evolved to attract pollinators with showy, colorful sepals. Such flowers are described as having a tepals condition, where sepals and petals are indistinguishable from each other.

Ecological Role

The primary ecological role of sepals is to protect the flower during its developmental phase. By encasing the more delicate parts of the flower, sepals prevent damage from environmental stresses such as wind, rain, and insect activity. Additionally, in some species, the sepals can contribute to the process of photosynthesis, much like leaves, due to their green pigmentation.

Evolutionary Significance

The evolution of sepals has played a crucial role in the diversification of flowering plants. Sepals have adapted in various ways across different species to enhance the survival and reproductive success of the plant. For instance, in some species, the sepals remain after the petals have fallen off to protect the developing fruit or to aid in seed dispersal mechanisms.

Cultural and Practical Uses

While sepals are primarily functional parts of the flower, they also have some applications in culinary and cultural contexts. For example, the sepals of the Roselle (Hibiscus sabdariffa) are used to make beverages and jams due to their high vitamin C content and distinct flavor.

See Also

• Petal
• Flower
• Calyx (botany)
• Tepals