As a bizarre thought: the ability to orbit a planet would make for some very interesting kinds of plants.
With no atmosphere between them and the sun, a plant could absorb vast quantities of light and grow to a collossal size.
A plant that always faces the sun could block it out, and provide food for an entire planet of nocturnal* species, as well as possibly being a source of mythology and worship for soceities of said species, due to the ridiculous size it could reach.
If it was in a different orbit, it would have a very intersting life-cycle, only opening its leaves while it's under the sun. Depending on it's orbit, this could be quite frequently, or only once a year or even longer. Would it bombard the planet with seeds after absorbing the amount of light it needs for energy? Would simply split into smaller plants? If, in it's infancy, it grew on the surface, how could it get into orbit?
It will be the plant editor that truly dooms us all. Aye, for one so overlooked, it wields terrible power.
*Is a species nocturnal if it lives on a planet where there is no daytime?