Every day I crossed the sunflower field on the way to work. It was a kind of short cut. When I first crossed the field, the tiny saplings did not interest me. It was not until I saw the giant sunflower standing on the stalk, that I began to take notice of the plant. I noticed several unique movements of the flower; the large flower head always chased the sun. Sometimes it almost twisted itself to catch the sun! Since many flowers are heliotropic and worship the sun, I was not unduly impressed. Yet, the large inflorescence always invited me to examine it closer.
It was a foggy day when I finally took time to examine the giant flower heads. Although most flowers opened in an inward wave, the neat rows of spirals were obscured by the irregular blooming florets.
The oldest flowers seemed to be at the edge, while the middle florets were the youngest. Small flower heads had about 21 spirals, while the larger ones had 34, 55, and I even counted 89 spirals in disbelief! What an impressive and compact way to pack large number of flowers!
What I learnt later in the library was even more fascinating. The number of spirals I had counted was a part of a larger series called Fibonnaci series. The numbers in this sequence are
1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 etc. Fibonnaci series is well known in mathematics. Although plants do not know about this, they just grow in the most efficient ways. Many plants show the Fibonacci numbers in the arrangement of the leaves, cones, and rings in the trunk. Pine and fir cones, daisies and sunflowers, and palm trees are other examples. Why does this arrangement occur? In the case of leaf arrangement, it may be related to maximizing the space for each leaf, or the average amount of light falling on each one. Even a small improvement could provide a dominant trait over many generations. In the case of close-packed leaves in cabbages and succulents the correct arrangement may be crucial for availability of space.
However, most of the spirals or leaf arrangement in nature are imperfect. That is because, nature isn't trying to use the Fibonacci numbers: they appear to be a by-product of a physical process. That is why the spirals are imperfect. The plant responds to physical constraints, not to a mathematical rule. If you are like me and want to know more about Fibonacci, you will have to head towards the library!