zygomorfi

Zygomorphy is a form of floral symmetry in which a flower can be divided into two mirror-image halves only along a single plane. This bilateral symmetry distinguishes it from actinomorphy, where a flower can be divided into equal mirror images along multiple planes. Zygomorphic flowers often exhibit specialized floral structures that guide or constrain how pollinators interact with the flower.

In many zygomorphic flowers, the corolla is modified into distinctive regions such as an upper lip and a lower lip, or a keel, which can enclose or position the reproductive organs. A well-known example is the papilionaceous corolla of many Fabaceae (the legume family), with a banner, two wings, and a keel that facilitates pollination. However, zygomorphy occurs across a range of angiosperm groups, including orchids and various members of Lamiales, and it is not restricted to a single lineage.

The ecological and evolutionary significance of zygomorphy lies in its association with pollinator interactions. Bilateral symmetry can direct a pollinator’s approach and contact with the flower’s reproductive parts, promoting more efficient pollen transfer and often favoring pollinator constancy. This can contribute to reproductive isolation and, in some groups, to rapid diversification.

Zygomorphy has evolved multiple times in flowering plants, leading to a mosaic distribution across taxa. Its presence is typically contrasted with actinomorphy, reflecting different evolutionary pressures related to pollination strategies and floral design. Examples of familiar zygomorphic flowers include Antirrhinum majus (snapdragon), many legume blossoms, and various orchids.