Magellum deltoids

The unidelta tree, closely related to the delta tree, has one important difference. Its leaves are not toxic but its roots are highly toxic. When these two trees are growing close together their roots form connections belowground. Through these connections the root toxin in the unidelta tree can pass to the delta tree, making its roots toxic as well. (Read more)
These two Magellum species have coevolved a mutualistic relationship that benefits them both. The unidelta tree shares its root toxin with the delta tree, which does not need to expend energy making its own, and the delta tree shares nutrients with the unidelta tree. The only clue that a transfer of toxin has occurred is a subtle change in the bioluminescent color of delta tree leaves at night, which the Na’vi have learned to identify. Animals have learned to avoid feeding on roots of both trees, making this mutualism an excellent defense for both plants.

The unidelta tree wood is harvested to make canoes, and the thick waxy leaf cuticle is melted down and used for additional waterproofing. The leaves themselves, which contain no toxic elements, are also used to make bowls since they are naturally waterproofed. The spines are used by the Na’vi to make tools as well as weapons for hunting and fishing.