From Ryzom Wiki
The plun is a very singular predator organism. Some botanists think that it is both animal and vegetable and shows a unique symbiosis on Atys. According to them the plun would be an animal that hosts a plant to function effectively. The transparent part would be an animal of the same family as the dziku which produces a light gas from the elements provided by the plant.
Unlike the dziku, mainly constituted of water, the plun would be filled by the same gas produced by the flyners of the Lakes and which gives it this lightness. The shimmering colours of the plun compared to the other plants of the Prime Roots would be a consequence of this symbiosis. The filaments hanging from the floating “stomach head” would be mouths in the same way as the balls of the lumindra.