taproot: (botany) main root of a plant growing straight downward from the stem
root: (botany) the usually underground organ that lacks buds or leaves or nodes; absorbs water and mineral salts; usually it anchors the plant to the ground
organophosphate nerve agent: any of a series of nerve agents containing organophosphate compounds first synthesized by German chemists in 1936; in World War II the Germans tested them in concentration camps but not on the battlefield; Iraq is alleged to have used them against Iran and against the Kurds