heliotropism
noun
he·li·ot·ro·pism ˌhē-lē-ˈä-trə-ˌpi-zəm 
: phototropism in which sunlight is the orienting stimulus
heliotropic
ˌhē-lē-ə-ˈtrō-pik
adjective -ˈträ-
Word History
Etymology
borrowed from French héliotropisme, from hélio- helio- + -tropisme -tropism, after héliotrope -tropism
Note: The term was probably introduced by the Swiss naturalist Jean Senebier (1742-1809) in Physiologie végétale, tome 3 (Geneva, 1800?), p. 182.
First Known Use
circa 1854, in the meaning defined above
Medical Definition
heliotropism
noun
he·li·ot·ro·pism ˌhē-lē-ˈä-trə-ˌpiz-əm
: phototropism in which sunlight is the orienting stimulus