or·tho·trop·ic 
(ôr′thə-trŏpĭk, -trōpĭk)
(ôr′thə-trŏpĭk, -trōpĭk)adj.
1. Growing toward or away from a stimulus such as gravity, especially along a vertical axis. Used of a plant or plant part.
2. Of or relating to a bridge deck consisting of steel plates supported by ribs underneath.
or′tho·tropi·cal·ly adv.
or·thotro·pism (ôr-thŏtrə-pĭz′əm) n.