Unique blue fruit’s colour does not fade even after a century!
The ‘brightest’ thing in nature, the Pollia condensata fruit, does not get its blue color from pigment but instead uses structural color – a method of reflecting light of particular wavelengths- new research reveals. This obscure little plant has hit on a fantastic way of making an irresistible shiny, sparkly, multi-colored, iridescent signal to every bird in the vicinity.
Most colors around us are the result of pigments. However, a few examples in nature – including the peacock, the scarab beetle and now the Pollia condensata fruit – use structural colors as well. Fruits are made of cells, each of which is surrounded by a cell wall containing cellulose. However, the researchers found that in the Pollia condensata fruit the cellulose is laid down in layers, forming a chiral (asymmetrical) structure that is able to interact with light and provide selective reflection of only a specific color. As a result of this unique structure, it reflects predominately blue light. The scientists also discovered that each individual cell generates color independently, producing a pixelated or pointillist effect (like those in the paintings of Seurat). This color is produced by the reflection of light of particular wavelengths from layers of cellulose in the cell wall. The thickness of the layers determines which wavelength of light is reflected. As a result, some cells have thinner layers and reflect blue; others have thicker layers and reflect green or red.
Because of how it is created, the color of the Pollia condensata fruit does not fade. The researchers found that samples of the fruit in herbarium collections dating back to the 19th century were as colorful and shiny as ones grown today.