Mistletoe has lost 'most of its respiratory capacity'. Most people know mistletoe as a plant to hang up and kiss under at the holidays. But in its natural environment, mistletoe is a hemiparasite, latching onto trees and extracting water and nutrients from them. Now, two independent studies show that mistletoe's parasitic lifestyle has brought about a surprising evolutionary loss. Mistletoe lacks key components of the cellular machinery other organisms depend upon to convert glucose into ATP. Source 6f.