Elements are interesting and I think plants illustrate that quite well as they utilize every element to some degree. Water, and through that water Earth is manipulated; the Fires of metabolism paired with the exchange of Air and kept in check by the power of Ice; its direction of growth driven by Light(ning). Of course there are stronger facets to plants such as water and earth, which comprise their form, but each would be required for full and complete manipulation of one. It can be read on the level of any of these- a water caster could determine good water flow, an earth caster could determine incoming and existing nutrition and composition, and so forth.
