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Yusuf Hamied Department of Chemistry

 

Image of Margaritaria nobilis courtesy Silvia Vignolini

Silvia Vignolini and colleagues have discovered that the iridescent colour of the fruits of Margaritaria nobilis originates from its cellulose cell structure. 

In a paper published in the Journal of the Royal Society Interface, the team describe how optical measurements revealed that the fruit’s bright and intense blue-green coloration is derived from the cellulose helicoidal cell wall structure in its outer layer of cells.

The skin of Margaritaria nobilis is made of cells, each of which is surrounded by a cell wall containing tiny cellulose fibrils. These fibrils form a helical structure in the cell wall of the fruit that interacts with light and reflects intense blue or green colouration.

”Cellulose is the same material that it is used to make cotton T-shirts and paper. It was amazing to discover how the cell wall of this fruit can use the same material that we use everyday for many applications to produce complex structures capable of reflecting such intense metallic colours,” pointed out Silvia, who conducted the study with scientists from Cambridge, the Royal Botanic Gardens Kew and the University of Exeter.

The same team reported a similar mechanism in the bright blue fruits of Pollia condensata in PNAS in 2012.  It is very surprising that these two species, which are not at all closely related and grow at opposite sides of the world, use the same mechanism to produce a similar metallic appearance.

“There is a lot still to learn about the diversity and evolution of fruit colour and how such amazing structures are made in nature, and this is our next challenge”, says Silvia.