The high-fly­ing physics of a plant’s ex­plod­ing fruits

Tehran Times - - SCIENCE -

When it’s time for the hairyflower wild pe­tu­nia to pass its genes to the next gen­er­a­tion, it does it with a bang.

To re­pro­duce, the plant flings tiny seeds from a small tor­pedo-shape fruit more than 20 feet through the air. That’s not an easy task.

The seeds are discs about a tenth of an inch in di­am­e­ter — smaller than the cir­cles that fall out of a hole punch — and 1/50th an inch thick, the equiv­a­lent of three sheets of pa­per.

“It’s like throw­ing con­fetti,” said Dwight Whi­taker, a pro­fes­sor of physics at Pomona Col­lege in Clare­mont, Calif.

In an ar­ti­cle pub­lished in the Jour­nal of the Royal So­ci­ety In­ter­face, Dr. Whi­taker and a trio of un­der­grad­u­ate physics ma­jors worked out what hap­pens in that mo­ment of ex­plo­sion that launches the seeds so far.

“It’s re­ally cool,” said Sheila Patek, a pro­fes­sor of bi­ol­ogy at Duke Univer­sity who was not in­volved with the re­search.

While sci­en­tists know that plants use a va­ri­ety of strate­gies to dis­perse seeds, Dr. Whi­taker and his stu­dents “re­ally did an ex­cep­tional job of show­ing how this comes to­gether in this par­tic­u­lar plant species,” Dr. Patek said.

Dr. Whi­taker be­came in­trigued with the hairyflower wild pe­tu­nia more than five years ago when botanists at Ran­cho Santa Ana Botanic Gar­den, less than a mile from cam­pus, told him about the plant.

The seeds sit within a small fruit that is a bit over an inch long. A spine along each half of the fruit is made of three lay­ers, which shrink at dif­fer­ent rates as they dry. That cre­ates a strain that bends them out­ward. The two halves re­main held to­gether by glue.

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