Fringe Science: are the corollas of Nymphoides (Menyanthaceae) flowers adapted for surface tension interactions?

摘要

Attractive features of flowers are adaptations for biotic interactions, and a few floral adaptations are for interactions with the physical environment. Marginal corollar appendages of Nymphoides (Menyanthaceae) can be membranous, a fringe of trichomes, or a ruffle. Although clearly enhancing display, a fringed corollar margin might function by generating a significant upward force through surface tension, an interaction adaptive in an aquatic environment. The force needed to dunk flowers with an intact corollar fringe and those whose fringe had been trimmed showed a significant difference. The fringe added a mean of 10.4% to the floral mass, but the upward force generated increased by nearly 50%, a significant difference from the predicted change based upon buoyancy alone. A correlation between plant form and type of corolla margin supports the surface-tension hypothesis. The membranous and ruffled corollar margins were found in species whose flowers had less risk of contacting the water's surface.