Bioluminescence is a way of living organisms to emit light. It is employed by nearly all Pandoran animals. Even the Na'vi have patterns of glowing dots that are unique to each individual. To avoid being detected by predators or pray, animals can damp down their own light. The RDA exploited it as another resource in the form of exotic jewelry and clothing.
Complete darkness is rare on Pandora. The large moon orbits a gas giant planet that in turn orbits a star with a stellar companion. Because of this unusual arrangement, most of Pandora's nights have some illumination; fully dark nights are few and far between. Thus, there was little evolutionary pressure on Pandoran fauna to develop night vision, echolocation, infrared sensors, or other methods of "seeing" in low-light conditions.
Some scientists theorize that nature found another way for Pandoran life forms to locate and identify one another. Bioluminescence, the production of "cold light" by living organisms, is employed by almost all Pandoran animals and plants to display their shape and location in the absence of external illumination. Even the Na'vi have patterns of glowing dots, which, like fingerprints, are unique to each individual. Anemonoid line the dense forest floors and waterways, providing the most light in the night landscape.
Most of Pandora's flora and fauna emits only one single color, often green, blue, indigo, or violet. There are exceptions like the Warbonnet Fern. Its leaves are illuminated by a broad band of red near their stems and by an iridescent blue near their tips. On Pandora, there is also a bioluminescent moss that is touch-sensitive. It will send out rings of blue-green light as a reaction to footsteps.
Bioluminescence is an enzymatic reaction that produces so called cold light. This reaction raises the valence electrons in the molecules of an organic compound to an orbit of higher energy. While decaying to its original state the electrons emit photons of visible light. It is a highly efficient reaction as it converts nearly all energy into light.
The reaction can occur within the metabolism of the creature or within symbiotic organisms that live inside of specialized organs, receiving food and oxygen from their host, and producing light in return.
There are several ways in which light production can be controlled:
* Limiting the availability of the involved chemicals
* The reaction takes place in an organ that can be moved away from the surface
* A translucent muscle carries the light from an internal organ to the surface by expansion and contraction
* Covering of the light producing area with dark pigment cells (melanophores)
A dark membrane that can be drawn over the light producing area