Many roads lead to the flower
There are many roads to Rome, or in this case to the flowers of plants like sunflower, gerberas and bellis. That is what researchers of the Przemyslaw Prusinkiewicz and Paula Elomaa groups show in the New Pathologist.
How the vascular tissues form remains an intriguing phenomenon. So far in plants this has been mainly studied in leaves, mainly because their relative simple 2D structure. But how the vasculature is organised in flowerheads, and especially flowerheads consisting out of multiple flowers was up till now mostly unknown. That the researcher decided to change.
The focussed on the flowerheads of the Asteraceae family. Starting with the flowerhead of the gerbera. They lay the flower in a CT-scanner. In this way they could study the vasculature in 3D without having to slice up the flower in many slices. They observed that the vasculature from the stem first bends outwards towards the edges of the flower, before that they bend inwards again just below the individual flowers. With each inward moving vein feeding multiple flowers.
Vasculature organisation in gerberas and bellis are two extremes of the same system
It was unexpected that the vasculature of gerberas was differently organised than what was known for sunflowers and bellis. To make sure that this was not a fluke of the new technique they used, they popped sunflower and bellis flowers in the CT-scanner as well. Confirming that the vasculature of the sunflower looks like that of gerberas, but then with more side branches. Those of bellis flowers looked more like a fine net positioned just below the surface of the flowers.
To check how the vasculature of other members of the Asteraceae family behaves, the researchers popped another five flowers in the CT-scanner: the thistle, the coneflower, the Tanacetum, the craspedia and the echinops. Those showed variations on the vasculature organisation shown by sunflowers and bellis.
It appears that the organisation of the vasculature by bellis and gerberas are two extremes of the same system. But with at least another 25000 family members, there always is a chance that one flower organised it vasculature completely different.
Literature
Owens, A., Zhang, T., Gu, P., Hart, J., Stobbs, J., Cieslak, M., Elomaa, P. and Prusinkiewicz, P. (2024), The hidden diversity of vascular patterns in flower heads. New Phytol. https://doi.org/10.1111/nph.19571
Plant en Zo 