Botanical Ballistics

Last week I received a letter from my dad that contained an interesting article from the Dec/Jan edition of NewScientist magazine (yes, my dad’s a scientist – a particle physicist, to be precise). It was entitled ‘Botanical Ballistics’, which was enough to catch my eye. But my dad’s hand-written note, telling us to “test this out with a suitable firearm” really caught my attention.  Hmmm…. a firearm??

So, what was the article about? As it turns out, several flowers open up so quickly that they’ve actually set a world speed record, up to 10,000 times faster than a rocket car (and definitely faster than a bullet leaves a rifle)!

The bunchberry dogwood is a perfect example of this. The flowers can only be cross-pollinated, so the trick is to get the pollen from one tree all the way to another tree. To facilitate this, the flowers have developed a remarkable way to fling their pollen straight into the air with such force that it sticks to passing insects, which then fly on to another tree with their load of pollen.  Here’s how it works…

As the flower matures, the stamens grow faster than the petals, causing the stamens to bend until eventually the middle is forced out between the closed petals (think of four elbows poking out). The pressure inside the flower continues to build as the stamens grow, and elastic energy builds up in the petals and flowers. Eventually, a flying insect comes along, hits a trigger hair on a petal, and BAM… the flower “explodes”. The petals burst apart and the stamens spring upwards like a catapult, carrying the pollen-loaded anthers with them. As the stamens reach maximum velocity, the anthems are released and flung upwards and the pollen is splattered all over the insect that triggered the explosion. Pretty neat, eh?

Other plants are also fast-action superheros, like the exploding spore capsules of sphagnum moss, the wood sorrel’s flip-action seed cannon, and the sperm-squirting liverwort. Researchers have captured incredible, slow-motion photos of some of these plants in action – definitely worth taking a look at if you can find the magazine.