The research, conducted at Harvard's School of Engineering and Applied Sciences (SEAS), contradicts earlier theories regarding growth within the flower bud. The petals, in fact, behave like leaves.
Published online in the journal Proceedings of the National Academy of Sciences, the findings characterize the blooming process using mathematical theory, observation and experiment.
"That differences in planar growth strains can lead to shape changes has been known for some time," says principal investigator L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics at SEAS. "But, showing that it is at work and dominant in lily blooming is new, as our measurements and simple theory show."
"What is most surprising is that a subject that is so rich in metaphor — the blooming of a flower — had been studied so little from a quantitative perspective."
Mahadevan collaborated with Haiyi Liang, formerly a postdoctoral fellow at SEAS and now a professor at the University of Science and Technology of China in Hefei. Together, they studied the asiatic lily Lilium casablanca, the bud of which comprises three inner petals wrapped in three outer sepals.
The findings contradict common assumptions about the lily, but they do seem to vindicate one unlikely theorist: German literary master Johann Wolfgang von Goethe.
In a 1790 essay, "Metamorphosis of Plants," Goethe proposed that petals and leaves could be homologous, meaning that they are both derived from one ancestral form.
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The work was partially funded by the National Science Foundation (NSF)-funded Materials and Research Science and Engineering Center at Harvard and the Defense Advanced Research Projects Agency (DARPA).