草莓污视频导航

April 15, 2021

International research collaboration solves centuries-old puzzle of pattern formation in flower heads

Faculty of Science computer scientists on team that advances fundamental understanding of plant biology
orange gerbera daisies

If you鈥檙e walking in a field of flowers this summer, look closely at the beautiful patterns in the flower heads. Figuring out how these distinctive and ubiquitous patterns form has puzzled scientists for centuries.

Now, an international team including 草莓污视频导航 researchers has solved the problem that stumped so many, including famed British mathematician, computer scientist and theoretical biologist Alan Turing.

The team鈥檚 five-year study focused on 鈥減hyllotaxis,鈥 the distribution of organs such as leaves and flowers on their supporting structure, which is a key attribute of plant architecture.

The formation of spiral phyllotactic patterns has been an open fundamental problem in developmental plant biology for centuries, due to the patterns鈥 role in defining plant form, says study co-author Dr. Przemyslaw Prusinkiewicz, PhD, professor in the in the .

鈥淲e have cracked this problem,鈥 he says.

The solution we provided is a contribution to basic science. But it was also a thrill to go after a difficult problem which many people couldn鈥檛 solve.

The collaboration involved Prusinkiewicz鈥檚 草莓污视频导航 research group and, from the University of Helsinki in Finland, a group led by Prof. Paula Elomaa.

The team combined tools unavailable to Turing 鈥 diverse genetic, microscopy and computational modelling techniques 鈥 to explain how phyllotactic patterns of flowers emerge in the flower heads of Gerbera hybrida, a member of the daisy family which also includes sunflower.

They found that phyllotactic patterns in gerbera, whose heads have large numbers (in the order of 1,000) of individual flowers, develop in a different way than patterns in plants with small numbers of organs. Scientists had previously explained those patterns in experimental model plants, such as Arabidopsis and tomato.

algorithmicbotany.org

But the team鈥檚 discovery of a novel developmental mechanism brings several new elements to the 鈥渢raditional鈥 theory of phyllotaxis.

鈥淭he patterning is not occurring in a static, pre-formed head structure. It occurs concurrently with the growth of the structure 鈥 when the flower head develops 鈥 and this plays a major role,鈥 Prusinkiewicz says.

The team鈥檚 , 鈥淧hyllotactic Patterning of Gerbera Flower Heads,鈥 is published as an open access paper in the Proceedings of the National Academy of Sciences of the USA.

Interdisciplinary collaboration key to discovery

Prusinkiewicz and his research group, which included study co-authors Dr. Mikolaj Cieslak, PhD, a senior research associate, and PhD student Andrew Owens, developed mathematical models based on experimental data obtained by the group at the University of Helsinki. 

鈥淭his was exemplary interdisciplinary research and international collaboration. Neither group could have obtained these results working alone,鈥 Prusinkiewicz notes.

The team found that phyllotactic patterns in gerbera are initiated by molecular processes, controlled by a plant hormone called auxin, taking place at the rim of the flower head. These processes occur long before any morphological (structural) changes can be seen.

As the flower head grows, new flowers are added between those previously formed as space becomes available, but they are shifted asymmetrically toward their older neighbouring flowers 鈥 producing a zigzag template for new flowers.

Prusinkiewicz research team

Research team, from left to right: Andrew Owens, Philmo Gu, Teng Zhang, Paula Elomaa, Przemyslaw Prusinkiewicz, Mikolaj Cieslak, Jeremy Hart, Alejandro Garcia.

Contributed

The team is the first to observe and report this asymmetry, and to show that it is key to the emergence of the phyllotactic patterns鈥 mathematical properties. For instance, the flowers are arranged in left- and right-winding spirals that typically occur in 鈥淔ibonacci numbers,鈥 where each number is the sum of the preceding ones: 1, 2, 3, 5, 8, 13, 21, 34, 55 . . ..

In a remarkable intersection between mathematics and biology, Fibonacci numbers also appear in the arrangement of leaves on the stems of many plants, the fruit sprouts of a pineapple, the flowering of an artichoke, and the arrangement of a pine cone鈥檚 scales.

Phyllotactic patterns are prevalent only in the plant kingdom, unlike simpler spiral patterns which are also found in some animals. There is no scientific consensus on why.

Prusinkiewicz subscribes to a theory that, from a plant鈥檚 perspective, it is easy and efficient to grow new flowers in this manner 鈥 as the space becomes available.

As a next step, the research team wants to see if the mechanism they discovered is present in a wide range of other plants. They also plan to use computational techniques to 鈥渓ook鈥 inside the flower heads, to connect the phyllotactic patterns visible from the outside with patterns of the plant鈥檚 inner vascular system.

The 草莓污视频导航 team鈥檚 research was funded by the and the through the housed at the University of Saskatchewan.