Sticky secretions from leaf hairs of Roridula plants help capture insect prey via a multi-step adhesive capture process.

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"Curious to find out exactly how R. gorgonias leaves ensnare their prey, Dagmar Voigt and Elena and Stanislav Gorb from the Max Planck Institute for Metals Research and Kiel University, Germany, decided to take a closer look at the hierarchy of hairs on R. gorgonias leaves…Voigt and her colleagues suspect that hapless insects fall foul of the plant's sticky leaves in a cascade of events. First, the insect brushes against, and sticks to, a long hair. As it begins to thrash around, it contacts more of the long hairs, becoming entangled in their sticky secretions. Next, it contacts the stiffer medium length hairs with intermediate strength adhesive and is finally trapped by the rigid short hairs with the strongest glue. Eventually the struggling insect runs out of energy and is immobilised." (Knight 2009:ii)

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"The flypaper trap of the protocarnivorous plant Roridula gorgonias is known to capture various insects, even those having a considerable body size, by using an adhesive, visco-elastic resinous secretion released by glandular trichomes of different dimensions. However, recent experimental studies have shown that the adhesion of long tentacle-shaped trichome secretion is not as strong as previously assumed. One may then ask why this flypaper trap is so highly effective. In the present study, we compared geometry, flexibility and the adhesive properties of secretion in different sized trichomes. We have analysed the gross morphology of the plant and its surfaces using light and cryo-scanning electron microscopy. Trichomes' stiffness and the adhesive properties of their secretion on different surfaces were measured. A combination of structural and experimental results, presented in this study, let us suggest that R. gorgonias represents a three-dimensional trap consisting of three functional hierarchical levels (plant, leaves and trichomes). According to their size, we classified three types of trichomes having a particular arrangement on the leaf. The longest trichomes are more flexible and less adhesive compared with the shortest ones. The latter are 48 times stiffer and their secretion has a 9 times higher adhesive strength. Our data support the hypothesis that the shortest trichomes are adapted to strong, long-term adherence to prey insects, and that the longest trichomes are responsible for initial trapping and entanglement function." (Voigt et al. 2009:3184)

Journal article
HAIR HIERARCHY HELPS R. GORGONIAS GET A GRIPJournal of Experimental BiologySeptember 11, 2009
K. Knight

Journal article
Hierarchical organisation of the trap in the protocarnivorous plant Roridula gorgonias (Roridulaceae)Journal of Experimental BiologySeptember 11, 2009
D. Voigt, E. Gorb, S. Gorb

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