Using Hibiscus trionum as a model to investigate development and ecological importance of floral diffraction gratings

The mutualistic relationship between pollinators and plants represents one of the most important interactions between animals and

plants. Floral traits of plants play pivotal roles in this interaction by serving as signals for attraction of pollinators. Structural colour

generated by diffraction gratings is one of the traits that have recently been discovered in diverse angiosperm species. Studies using

artificial flowers have demonstrated that optical effects generated by floral diffraction gratings are salient to the model pollinator

Bombus terrestris. However, how diffraction gratings are established during development of plants and whether this trait is

ecologically important to plants by attracting pollinators in natural conditions remain to be investigated. To explore development of

this trait, Hibiscus trionum has been established as a novel model plant and its floral diffraction gratings have been discovered as

results of nanoridges in cuticles covering petal epidermal cells. It was further proposed that during development the cuticle proper

undergoes isotropic expansion whereas the underlying extracellular matrix (ECM) expands anisotropically, so that in-plane

compressive stress is induced to give rise to cuticular ridges. In this study, I will alter stiffness of the cuticle proper and ECM of

H.trionum petal epidermal cells by genetically manipulating relevant genes to investigate how material properties of these two layers

contribute to formation of diffraction gratings. The transgenic lines to be developed are expected to have altered diffraction gratings

but keep other floral traits unchanged. These lines will be analysed for effects of the diffraction gratings on pollinator behaviour.

Findings from this study will not only promote understanding of development and ecological importance of diffraction gratings in

H.trionum, but also lay a foundation for investigation of the convergent evolution of this trait in diverse angiosperm species.