- News Home
17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
- About Us
ScienceShot: Unraveling the Mystery of Self-Planting Seeds
6 June 2012 2:20 pm
When it comes to sowing seeds, some plants only have to drop them and let gravity take care of the rest. But seeds from a family of small flowering plants known as Geraniaceae, give themselves a helping hand: after bursting open from beak-shaped fruits, they literally drill themselves into the ground. Scientists have long known that this bursting and drilling results from hairy appendages on the seeds called awns, which coil up and straighten out with changes in humidity, slowly propelling the seeds downward. Now, researchers have figured out the structural changes occurring in the cells of these awns that generates the coiling mechanism. The scientists began by creating a mathematical model of an awn cell—a rod-shaped structure wrapped in rigid, helical fibers. They described these helices with two parameters, the so-called mean angle and tilt angle of the fibers, and found that if these didn't change as the cell shrunk due to lowering humidity, the cell would have to respond by taking on its own spiral shape. Likewise, the cell would straighten out as soon as humidity rose again, creating the drilling motion. To test its model, the team predicted values for the mean and tilt angles for two species of the Geraniaceae family—one commonly known as stork's bill (Erodium cicutarium, pictured) and the other as cranesbill (Geranium pusillum)—that would produce the observed coiling. The results of x-ray measurements of real awn cells closely matched the predictions, demonstrating that the coiling does indeed arise from the arrangement of the outside fibers. The researchers say their results, published this week in Physical Review Letters, could help engineers build materials that change their configuration with the environment, such as new types of catheters that automatically bunch up to unblock obstructed blood vessels.
See more ScienceShots.