Flower Sets Catapult Speed Record
An American team of two biologists and a physicist found that a common mountain flowering plant holds the plant acceleration record. Reporting in Nature,1 they calculated that the bunchberry dogwood flower propels its pollen at speeds approaching 14 mph when the catapult-like petals explode open, accelerating at 24,000 meters per second squared within 0.3 second. The pollen is thus launched, against air resistance, to 10 times the height of the flower.
Medieval kings waging war could have learned something from these little flowers:
Bunchberry stamens are designed like miniature medieval trebuchets – specialized catapults that maximize throwing distance by having the payload (pollen in the anther) attached to the throwing arm (filament) by a hinge or flexible strap (thin vascular strand connecting the anther to the filament tip). This floral trebuchet enables stamens to propel pollen upwards faster than would a simple catapult. After the petals open, the bent filaments unfold, releasing elastic energy. The tip of the filament follows an arc, but the rotation of the anther about the filament tip allows it to accelerate pollen upwards to its maximum vertical speed, and the pollen is released only as it starts to accelerate horizontally. (Emphasis added in all quotes.)
The bunchberry is incapable of self-pollination, so it needs insects that rapidly move from flower to flower. They figure that the mechanism favors heavy pollinators like bumblebees to release the catapult, and favors either large flying insects or wind pollinators instead of slow-moving insects like ants.
This speed record exceeds the snap of the Venus flytrap, the strike of the mantis shrimp, and even the leap of the froghopper (see 08/01/2003 story).
1Edwards et al., “Botany: A record-breaking pollen catapult,” Nature 435, 164 (12 May 2005) | doi: 10.1038/435164a.
The authors make no mention of how this mechanism evolved, but do use the word design. Presumably, they believe the design preceded the medieval crusades. For organisms rooted to one spot, plants sure have some amazing ways of getting around.