The "Tree of Mana/Tree of Life" plot worked so well in FFA, that they decided to continue with the SaGa series. They were going to go with an underground crystal cave, but someone mentioned either Romancing SaGa or SaGa Frontier in a passing conversation, and they ended up with the Iifa Tree. So if it weren't for Seiken Densetsu being remade as Final Fantasy Adventure/Mystic Quest, we would have had a crystal cavern or something instead of a mist-filled Yggdrasil. Not a reference, but pretty awesome.