Sunflowers show complex Fibonacci sequences
Crowdsourced data finds patterns more complicated than ever reported
By John Bohannon
Science.org
Sept 17, 2022
Excerpt:
Mathematical biologists love sunflowers. The giant flowers are one of the most obvious—as well as the prettiest—demonstrations of a hidden mathematical rule shaping the patterns of life: the Fibonacci sequence, a set in which each number is the sum of the previous two (1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, …), found in everything from pineapples to pine cones. In this case, the telltale sign is the number of different seed spirals on the sunflower’s face. Count the clockwise and counterclockwise spirals that reach the outer edge, and you’ll usually find a pair of numbers from the sequence: 34 and 55, or 55 and 89, or—with very large sunflowers—89 and 144.
Although the math may be beautiful, plant biologists have not worked out a mechanistic model that fully explains how the sunflower seed patterns arise. The problem is that plants don’t always show perfect Fibonacci numbers—real life is messy—and data on real sunflower diversity is scarce. So the Museum of Science and Industry in Manchester, U.K., crowdsourced the problem. Over the past 4 years, members of the public have been growing their own sunflowers and submitting photographs and counts of the spiral patterns.
