Pollen from bunchberry flowers are dispersed by release of stored elastic energy.

"The petals restrain the four stamens that are bent in the bud and store elastic energy used to launch pollen. Each stamen consists of a filament with a pollen-containing anther sac attached with a hinge to the filament tip. The anther sacs dehisce or split open before the flower blooms and are ready to propel pollen as soon as the flower is triggered open." (http://www.williams.edu/go/explodingflower/plant.html)

"These amazing flowers can bloom in under 0.4 ms--a time shorter than it takes for a bullet to travel the length of a rifle barrel. To our knowledge this is the fastest flower on earth. Pollen is accelerated at 24,000 m/s², which is 2400 times the acceleration of gravity and 800 times that experienced by astronauts during liftoff. Pollen leaves the plant with an initial velocity of more than 4 m/s and is propelled an impressive 2.5 cm into the air, over ten times the height of the flower.

"Explosive flowering enhances insect pollination in two ways. First explosive flowering reduces the amount of pollen eaten by the insects because the pollen spray from the explosion disperses the pollen on insects' bodies and the high speed of the pollen imbeds it deep in the insects' hairs where it is less likely to be gathered and eaten. Second, explosive flowering limits pollinators to insects heavy enough to trigger the flower. Large flies, bumblebees and beetles are large enough to trigger flowers and move rapidly between inflorescences, whereas ants and small flies, which often stay on one inflorescence, cannot trigger the flowers." (http://www.williams.edu/go/explodingflower/)

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"[W]e describe how the flower stamens of the bunchberry dogwood (Cornus canadensis) rely on this principle [release of stored elastic energy] to catapult pollen into the air as the flower opens explosively. Our high-speed video observations show that the flower opens in less than 0.5 ms — to our knowledge, the fastest movement so far recorded in a plant.
"Cornus canadensis grows in dense carpets in the vast spruce-fir forests of the North American taiga. As bunchberry flowers burst open, their petals rapidly separate and flip back to release the stamens (Fig. 1). During the first 0.3 ms, the stamens accelerate at up to 24,000 + or - 6,000 m/s2 (2,400g), reaching the high speed (3.1+ or - 0.5 m/s) necessary to propel pollen, which is light and rapidly decelerated by air resistance (terminal velocity, 0.12 + or - 0.03m/s(mean = or - s.e.m.);n=7).The? pollen granules are launched to an impressive height of 2.5 cm (range, 2.2–2.7 cm; n=5), which is more than ten times the height of the flower: from this height, they can be carried away by the wind."

"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 tipof 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. (Edwards et al. 2005:164)

Journal article
Botany: A record-breaking pollen catapultNatureDecember 5, 2005
Joan Edwards, Dwight Whitaker, Sarah Klionsky, Marta J. Laskowski

Bunchberry DogwoodCornus canadensisSpecies