Editing Common sunflower (section)

==== Floret arrangement ====
Generally, each floret is oriented toward the next by approximately the [[golden angle]], 137.5°, producing a pattern of interconnecting [[spiral]]s, where the number of left spirals and the number of right spirals are successive [[Fibonacci number]]s. Typically, there are 34 spirals in one direction and 55 in the other; however, in a very large sunflower head there could be 89 in one direction and 144 in the other.<ref>{{Cite book |last1=Adam |first1=John A. |year=2003 |title=Mathematics in Nature: Modeling Patterns in the Natural World |url=https://books.google.com/books?id=2gO2sBp4ipQC&q=large-sunflower+spirals+144+89&pg=RA1-PA217 |via=[[Google Books]] |access-date=31 January 2011 |location= Princeton, New Jersey |publisher= Princeton University Press | page=217 |isbn=978-0-691-11429-3 }}</ref><ref>{{cite web |url=http://www.mcs.surrey.ac.uk/Personal/R.Knott/Fibonacci/fibnat2.html#demos |title= Fibonacci Numbers and Nature - Part 2 |first1= Ron |last1= Knott |website=Department of Computer Science |publisher = [[University of Surrey]] |date=12 February 2009 |access-date=31 January 2011 |url-status=dead |archive-url=https://web.archive.org/web/20090916234127/http://www.mcs.surrey.ac.uk/Personal/R.Knott/Fibonacci/fibnat2.html#demos |archive-date=16 September 2009 }}</ref><ref>{{cite web |url=http://www.mcs.surrey.ac.uk/Personal/R.Knott/Fibonacci/fibnat.html |last1=Knott |first1=Ron |title= Fibonacci Numbers and Nature |website=Department of Computer Science |publisher = University of Surrey |date=30 October 2010 |access-date=31 January 2011 |url-status=dead |archive-url=https://web.archive.org/web/20090907063800/http://www.mcs.surrey.ac.uk/Personal/R.Knott/Fibonacci/fibnat.html |archive-date=7 September 2009 }}</ref> This pattern produces the most efficient packing of seeds mathematically possible within the flower head.<ref>{{Cite book|url=https://books.google.com/books?id=f_VMeAToefwC&q=fibonacci+packing+efficiency&pg=PA154|title=Introduction to landscape design |last1=Motloch |first1=John L. |year=2000 |access-date=31 January 2011 |location = New York, USA | publisher= John Wiley & Sons, Inc. |page=154 |isbn=978-0-471-35291-4 }}</ref><ref>{{Cite book|url=https://archive.org/details/phyllotaxissyste0000jean/page/185 |url-access=registration |page= 185 |quote=fibonacci packing efficiency. |title=Phyllotaxis |access-date=2011-01-31|isbn=978-0-521-40482-2|last1=Jean|first1=Roger V|year=1994|publisher=Cambridge University Press }}</ref><ref>{{cite web|url=http://www.geocities.com/capecanaveral/lab/5833/cycas.html |title=Parastichy pair(13:21) of CYCAS REVOLUTA (male) florets_WebCite |url-status=dead |archive-url=https://web.archive.org/web/20091003194946/http://www.geocities.com/capecanaveral/lab/5833/cycas.html |archive-date=3 October 2009 }}</ref>

A model for the pattern of [[floret]]s in the head of a sunflower was proposed by H. Vogel in 1979.<ref>{{Cite journal |last=Vogel |first=H. |title=A better way to construct the sunflower head |journal=Mathematical Biosciences |volume=44 |issue=3–4 |pages=179–189 |year=1979 |doi=10.1016/0025-5564(79)90080-4 }}</ref> This is expressed in [[polar coordinates]]
:<math>r=c \sqrt{n},</math>
:<math>\theta=n \times 137.5^{\circ},</math>
where θ is the angle, ''r'' is the radius or distance from the center, and ''n'' is the index number of the floret and ''c'' is a constant scaling factor. It is a form of [[Fermat's spiral]]. The angle 137.5° is related to the [[golden ratio]] (55/144 of a circular angle, where 55 and 144 are Fibonacci numbers) and gives a close packing of florets. This model has been used to produce computer generated representations of sunflowers.<ref>{{cite book |last1=Prusinkiewicz |first1=Przemyslaw |author-link=Przemyslaw Prusinkiewicz |last2=Lindenmayer |first2= Aristid |author-link2=Aristid Lindenmayer |title=The Algorithmic Beauty of Plants |publisher=Springer-Verlag |year=1990 |url= https://archive.org/details/algorithmicbeaut0000prus/page/101 |pages=101–107 |isbn=978-0-387-97297-8 }}</ref>

{{gallery|mode=packed
|Sunflower macro wide.jpg|Detail of disk florets
|Solros - Sunflower (Helianthus annuus) - Ystad-2024.jpg|After flowering, the  seeds are visible.
|Sunflower (Helianthus annuus) seeds.jpg|Sunflower seeds
}}