Lily, as a symbol of pure, solemn and beauty, whose literary history can be traced back 3,000 years BC, to ancient Egypt. However, people know little about how the Lily blooms. Scientists have revealed that the lateral differential growth of petals provide the underlying forces that drive the lily's bloom.
On Mar 21, the journal "Proceedings of the National Academy of Sciences" published the findings which characterize the blooming process using a combination of mathematical theory, observations, and experiments. Prof. LIANG Haiyi collaborated with Mahadevan, Professor of Harvard University, demonstrated the mystery of the lily blossom. They used a camera recording the complete process of a lily blooming and found the following results.
"The traditional view holds that the midrib of lily petals will bend outwards, or the inner surface of petals grow faster than the outside (i.e the double metal bending mechanism), which drives the blooming of a lily. Dr. LIANG Haiyi, a "Hundred Talents" Professor of Department of Modern Mechanics, USTC, said, "initially the statements above look reasonable, but after close examination, you find the deficiency in the original views explained within the gradual forming of wrinkles created along the edge of the petals. "
The scientists marked lily buds with dots along each petal's edge and midrib or central vein, to measure changes in the size and shape of the flower, as it went from bud to bloom. They immersed the stem of a lily (Lilium Casablanca) in water, and filmed it for four and a half days until the flower fully opened. The video revealed that the edges of the petals grow up to 40 percent more than the interior midrib. So the scientists came to a conclusion that the differential growth of the petals create a compression along the edge while a tension in the midrib; petals in this uneven growth cause internal forces to gradually bend petals, creating waves and finally the bloom.
Further theoretical and numerical simulations reveal in detail, the internal forces within the flower petals. The Scientists were surprised to find, in the early stage of blooming, that the petal bends slowly, but after it reaches a certain critical point, the petal bends faster to complete the blossom.
"In 1790, the German naturalist Johann Wolfgang von Goethe prophesied in his essay of 'Change in the Plant', "a paper claim leaves and flowers are homologous". Our previous work showed that the edge of the overgrowth is the key in determining the shape of leaves. The fact that leaves and lilies have the identical mechanism, offers evidence to the observations of von Goethe," LIANG said, " Nature once again demonstrates a highly evolved example, offering us a brand new design principle for bionics."
(Department of Modern Mechanics of USTC, News Center of USTC)