Understanding capitulum development: Gerbera hybrida inflorescence meristem as an experimental system

Inflorescences, the flower-bearing structures in plants, show enormous diversity in nature. Their architecture, in terms of number and arrangement (phyllotaxis) of flowers, play a central role in reproductive success and adaptation of plants, as well as yield in crops. We apply Compositae capitula, or flower heads, as our model system to study inflorescence development. The unique architecture of capitula, often composed of morphologically and functionally distinct types of flowers, is considered the key innovation for the evolutionar y success of this largest family of flowering plants. Moreover, the arrangement of individual flowers in intersecting spirals in capitula represent an iconic example of the geometric regularity found in nature. Our aim is to explore the gene regulator y networks that control patterning of the Compositae inflorescence meristems and their subsequent development. In this brief review, we summarize the recent technological developments and tools that allow us to explore and follow meristem patterning early on – already before we can see any visual changes in them. These include visualization of capitulum development by X-ray micro-computed tomography (micro-CT), live-imaging of dissected meristems on tissue culture media, and application of laser ablation to disrupt meristem organization and to follow its re-patterning. We anticipate that these methods are applicable to distinct species to promote comparative studies and understanding of developmental diversity of capitula within Compositae.