Spur (botany)

Spur (botany)

A flower of Utricularia sandersonii showing a prominent spur.

In botany, a spur is a tubular outgrowth of tissue on a plant, often found on flowers or fruit. Spurs are typically associated with the nectary and serve to hold nectar, attracting pollinators such as insects and birds. The presence of a spur can influence the pollination mechanism and the type of pollinators that visit the flower.

Structure and Function

Spurs are usually formed by the extension of the petals or sepals, creating a hollow, elongated structure. The primary function of a spur is to store nectar, which is a sugary liquid produced by the plant to attract pollinators. The shape and length of the spur can vary significantly among different plant species, often correlating with the pollinator's morphology. For example, flowers with long spurs may be pollinated by hummingbirds or moths with long proboscises, while shorter spurs may attract bees or butterflies.

Evolutionary Significance

The evolution of spurs is a classic example of coevolution between plants and their pollinators. As pollinators evolve to exploit the nectar within spurs, plants may evolve longer or differently shaped spurs to better accommodate their pollinators. This mutualistic relationship can lead to a high degree of specialization, with certain plants being pollinated by specific pollinators.

Examples in Nature

Spurs are found in a variety of plant families, including the Ranunculaceae, Orchidaceae, and Violaceae. In the Ranunculaceae family, the genus Aquilegia, commonly known as columbines, is well-known for its distinctive spurred flowers. The length and curvature of the spurs in Aquilegia species are adapted to different pollinators, such as bees, hummingbirds, and hawkmoths.

In the Orchidaceae family, many orchids have spurs that are integral to their pollination strategies. The Angraecum orchid, for example, has a long spur that is pollinated by the hawk moth with an equally long proboscis.

Related Pages

• Pollination
• Nectar
• Coevolution
• Orchidaceae
• Ranunculaceae