Pitcher geometry facilitates extrinsically powered ‘springboard trapping’ in carnivorous Nepenthes gracilis pitcher plants

Carnivorous pitcher plants capture insects in cup-shaped leaves that function as motionless pitfall traps. Nepenthes gracilis, evolved a unique ‘springboard’ trapping mechanism that exploits the impact energy of falling raindrops to actuate a fast pivoting motion of the canopy-like pitcher lid. We superimposed multiple computerized micro-tomography images of the same pitcher to reveal distinct deformation patterns in lid-trapping N. gracilis and closely related pitfall-trapping N. rafflesiana. We found prominent differences between downward and upward lid displacement in N. gracilis only. Downward displacement was characterised by bending in two distinct deformation zones while upward displacement was accomplished by evenly distributed straightening of the entire upper rear section of the pitcher. This suggests an anisotropic impact response, which may help to maximize initial jerk forces for prey capture, as well as the subsequent damping of the oscillation. Our results point to a key..., Dataset 1
N. gracilis (n = 6) and N. rafflesiana (n = 5) pitchers were freshly harvested and CT-scanned immediately.
To this end, they were embedded up to a third of their height in an upright position in a container filled with sand, and the sand was moistened to solidify and keep the pitchers in place. The lid of the container had a custom-built mechanism that was attached to the lid of the pitcher and allowed to manipulate the lid position in between scans (neutral lid position, pushed down lid and pulled up lid). Each pitcher was scanned in a computerized tomography scanner (Nikon XT H 225 ST, Nikon Metrology Inc., Brighton, US). Scans were conducted with 3141 projections, 70 kV, 354 ms exposure time, without averaging over multiple scans and resulted in a voxel size of 30 µm (all N. gracilis and 1 N. rafflesiana pitcher) and 38 µm (all other N. rafflesiana pitchers). Scan time was limited to 20 minutes per scan to minimize dehydration of the tissue.
The three image stacks of the sa..., Dataset 1 includes (1) 33 CT scans as *.tif stacks and their scanning information; (2) coordinate data that was extracted from the CT scans as *.csv-files; (3) a python-script to analyse the coordinates and calculate curvature and visualise the data; and (4) an additional python-script to summarize this data.
Dataset 2 includes 20 overlaid jpg-images to measure lid displacement and the *.xlsx-file that summarises the measurements and data analysis for this data.
Further instructions are in the README.txt
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