Journal
ROYAL SOCIETY OPEN SCIENCE
Volume 3, Issue 5, Pages -Publisher
ROYAL SOC
DOI: 10.1098/rsos.160091
Keywords
Fibonacci phyllotaxis; parastichy number; sunflower Helianthus annuus; citizen science
Categories
Funding
- Museum of Science and Industry, Manchester
- Manchester City Council
- Granada Foundation
- Kirby Lang Foundation
- Oglesby Charitable Trust
- Eastland Homes
- RSA NorthWest Fellowship
- Wellcome Trust Engagement Fellowship [WT099887MA]
- Life Sciences Impact Award from the Faculty of Life Sciences at the University of Manchester
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This citizen science study evaluates the occurrence of Fibonacci structure in the spirals of sunflower (Helianthus annuus) seedheads. This phenomenon has competing biomathematical explanations, and our core premise is that observation of both Fibonacci and non-Fibonacci structure is informative for challenging such models. We collected data on 657 sunflowers. In our most reliable data subset, we evaluated 768 clockwise or anticlockwise parastichy numbers of which 565 were Fibonacci numbers, and a further 67 had Fibonacci structure of a predefined type. We also found more complex Fibonacci structures not previously reported in sunflowers. This is the third, and largest, study in the literature, although the first with explicit and independently checkable inclusion and analysis criteria and fully accessible data. This study systematically reports for the first time, to the best of our knowledge, seedheads without Fibonacci structure. Some of these are approximately Fibonacci, and we found in particular that parastichy numbers equal to one less than a Fibonacci number were present significantly more often than those one more than a Fibonacci number. An unexpected further result of this study was the existence of quasi-regular heads, in which no parastichy number could be definitively assigned.
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