"Designating or relating to a plant part or organ that tends to take up an oblique or horizontal position with relation to the main axis, usually because its own parts react differently to the influence of external stimuli (such as light, gravity, etc.). Contrasted with orthotropic", Late 19th cent.; earliest use found in Sydney Vines (1849–1934), botanist. From plagio- + -tropic, after German plagiotrop.[plagiotropic etymology, plagiotropic origin, 英语词源]