sympetaly

Sympetaly refers to the fusion of petals in a flower. This fusion can occur at the base, along the entire length, or in various degrees between these extremes. Flowers with unfused petals are described as apopetalous, while those with fused petals are sympetalous. This characteristic is a significant feature in plant classification, often used to distinguish between major plant groups. For example, sympetaly is a common trait found in dicotyledonous plants, particularly within the asterid and rosid clades.

The degree of fusion can vary greatly. In some species, the petals are only fused at their very base, forming a short tube. In others, the fusion extends much further up the petal, creating a distinct corolla tube with free lobes at the apex. The appearance of the fused petals can range from a simple, bell-shaped structure to more complex forms with elaborate lobes or spurs. The development of sympetaly is thought to be an evolutionary adaptation, potentially offering advantages such as increased pollination efficiency by attracting specific pollinators or by providing a more protected nectar source. The fused petals can create a more robust structure, better able to support the weight of larger insects or to form a landing platform. Furthermore, the shape of the sympetalous corolla can influence which pollinators can access the flower, contributing to reproductive isolation and the evolution of specialized pollination syndromes.