There are two groups of equiangular spirals in the sunflower disk, one is coiled clockwise, the other is coiled counterclockwise, and they are nested with each other.

Although the number of these positive and negative spirals is not fixed in different sunflower varieties, it often does not exceed three groups of numbers: 34 and 55, 55 and 89 or 89 and 144.

In fact, the two opposite isometric spirals of sunflower are two adjacent terms in Fibonacci sequence, usually 2 1 counterclockwise and 34/clockwise; Or counterclockwise 34 and clockwise 55, the spiral number of the larger sunflower family is 89, 144. Pine cones and pineapples have a similar pattern. The former has five and eight family helices, while the latter has eight and 13 family helices.

Principle of sunflower equiangular spiral

The equiangular spiral of sunflower is consistent with the golden spiral in mathematics. The reason why sunflowers are arranged like Fibonacci series is that the arrangement of golden spiral can accommodate more florets in the same area, so in the long evolution process, the arrangement of sunflower florets is getting closer and closer to the spiral.

In addition to the isosceles spiral of sunflower showing the nature of Fibonacci series, Fibonacci series has many applications in nature. By observing the petals of Trillium, Rosa davurica, Sanguisorba americana, cosmos, Jin Fenghua, funnel vegetables, lilies and iris, we can find that their petals also have Fibonacci numbers.