d.kirkup at LION.RBGKEW.ORG.UK
Fri Jan 23 15:13:32 CST 1998
The following may be of interest;
Karl Niklas (in "Plant Biomechanics" , Chicago 1992) mentions differential
tensile stress in the tissues of the fruits of Impatiens and Oxalis spp which
may propel the seeds up to 3m vertically. He also gives a figure for the velocity
of expulsion of the seeds of the prickly cucumber (Echinocystis lobata) as
"exceeding 11.5 meters per second" as a result of the build up of hydrostatic
Job Kuijt (in "The Biology of Parasitic Flowering Plants", California 1969) cites
studies by Hinds and Hawksworth in which the speed of the explosively dispersed
seeds of several Dwarf Mistletoes (Arceuthobium spp.) were calculated to have
initial velocities of c. 24 meters per second (not quite 60 mph). The seeds are
only about 3 mm long and were expelled an average distance of c. 5 meters, but
sometimes reached nearly 15 meters.The figures were obtained using photography.
On a slightly different note, the flowers of most tropical Loranthaceous
mistletoes open explosively to shed pollen, sometimes so violently that the
stamens become detached.
Doug Yanega wrote:
> Mary Barkworth asked:
> >someone knows of a faster seed, I would like to hear of it.
> I could swear I've heard that some mistletoes fired their seeds tens of
> meters, and that they were coated with a glue-like substance so they would
> stick where they hit. That would imply a pretty high velocity. I doubt the
> coiled-spring pods of legumes like Lathyrus generate quite 60 mph shots,
> and definitely not pods like Oxalis or Impatiens. But I do wonder how one
> goes about measuring the speed, exactly.
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