heliotropism noun. [,hi:lɪǝ(ʊ)'trǝʊpɪz(ǝ)m] M19.
[from HELIO- + Greek -tropos turning + -ISM.]
Botany. The property of growing in a given direction in response to sunlight; esp. (in full positive heliotropism) growth towards the light. Also negative heliotropism, growth away from the light; transverse heliotropism, growth in a direction at right angles to the light.

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