posted on Sep, 11 2012 @ 07:19 AM
This odd fruit have really extraordinary iridescent colours that are not the result of pigmentation.
Indeed, Pollia condensata fruit, does not get its blue colour from pigment but instead uses structural colour – a method of reflecting light of
In the forests of central Africa, there’s a plant that looks like it’s growing its own Christmas decorations. Shiny baubles sprout from between
its leaves, shimmering in a vibrant metallic blue. Look closer, and other colours emerge – pinpricks of red, orange, green and violet. It looks as
if Seurat, or some other pointillist painter, had turned their hand to sculpture.
But these spheres, of course, are no man-made creations. They’re fruit. They are the shiniest fruits in the world. Actually, they are the shiniest
living materials in the world, full-stop.
Most colours 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 colour 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 colour. As a result of this unique
structure, it reflects predominately blue light.
The color is caused by Bragg reflection of helicoidally stacked cellulose microfibrils that form multilayers in the cell walls of the epicarp. The
bright blue coloration of this fruit is more intense than that of any previously described biological material.
Uniquely in nature, the reflected color differs from cell to cell, as the layer thicknesses in the multilayer stack vary, giving the fruit a striking
pixelated or pointillist appearance. Because the multilayers form with both helicoidicities, optical characterization reveals that the reflected light
from every epidermal cell is polarized circularly either to the left or to the right, a feature that has never previously been observed in a single