Even by invading plants' standards, the filaree, or common stork's bill, has been remarkably successful. Introduced into North America in the eighteenth century, it is now endemic in south-western states such as California, and the plant's intriguing seed dispersal mechanism seems to lie at the root of their success.
Having launched as far as possible from the mother plant, the seed drills itself into the ground by repeatedly curling and unwinding a strap-like structure, known as an awn, to give it the best chance to germinate. But how do they self-drill? Having watched the seeds bore themselves into the ground in California, research associate Scott Hotton took them back to Jacques Dumais' Harvard laboratory to take a closer look and when Dumais set his introduction to botany class the challenge of making a time-lapse movie, Dennis Evangelista jumped at the opportunity to film the seed's drilling action.
Evangelista, Hotton and Dumais publish their discovery that filaree seeds are launched with a spring mechanism that also drills the seeds into the ground in The Journal of Experimental Biology at http://jeb.biologists.org/cgi/content/abstract/214/4/521.
Setting up a camera in his kitchen, Evangelista wet the dry seeds and filmed them as they uncurled and then rewound when they dried. Evangelista explains that when humidity is low the awn dries, curls and drills the seed into the soil. When the humidity rises the awn uncurls, but backward facing hairs on the awn force the seed to move in one direction so that it continues drilling into the ground even when it uncurls. Plotting the tip's trajectory as it wound round, Evangelista realised that the awn behaved like a beam bending into a stretched logarithmic spiral. He could use engineering physics to calculate the amount of energy stored in the awn as it ripened and dried within the fruit and use it to explain how the seeds launch themselves. 'By knowing how much energy is in the dry awn when it is held straight in the seed head I can estimate the range that it goes,' says Evangelista; but first he needed to find out just how far the seeds could fly.
Setting up a high speed camera in Mimi Koehl's Berkeley laboratory and filming seed heads – formed from clusters of five awns – Evangelista captured the instant when an awn finally tore loose and the speed as it catapulted free, launching the seed up to 0.5m from the plant. But how well would Evangelista's energy storage model hold up when he used it to calculate how far the seed could be launched?
Calculating the amount of energy that was released as the dry awn curled and broke free of the seed head, Evangelista then subtracted the amount of energy required to tear the awn away and the energy lost to wind resistance as the seed tumbled through the air, before calculating the distance that the seed could be flung. His calculations matched the distance that the filmed seed had flown. So filaree seeds disperse by using energy stored in the dry awns, which act as springs to fling the seeds by up to 0.5m.
Having discovered how filaree seeds are so successful at propagating, Evangelista and Dumais are now keen to find out how other members of the geranium family disperse their seeds. Evangelista explains that all geraniums are thought to use variations of the awn catapult mechanism for seed dispersal and propagation and he is keen to find out how changes in the awn's material properties affect seed dispersal in other members of the geranium family.
IF REPORTING ON THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org
REFERENCE: Evangelista, D., Hotton, S. and Dumais, J. (2011). The mechanics of explosive dispersal and self-burial in the seeds of the filaree, Erodium cicutarium (Geraniaceae). J. Exp. Biol. 214, 521-529.
This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT firstname.lastname@example.org
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine